§ 


0L- 


LIBRARY 

OF   THE 

UNIVERSITY  OF  CALIFORNIA. 


PACIFIC  THEOLOGICAL  SEMINARY. 

.84529 


Class  Book 

Accession  No.' 


LIBRARY 

GIFT  OF 


_,  '\ 
"\ 


^ 


FIEST  PEINCIPLES 


or 


CHE1ISTEY, 


FOB  THE 


Is*  0f 


BENJAMIN  SILLIMAN.  JR..  M.A..  M.D. 

niOFKSSOR   IN  TALE  COLLEGE   OF  CHEMISTRY  AS  APPLIED  TO  THE  ARTS,  AND  OF  MEDIOAC 
CHEMISTRY  A»D  TOXltJOLOGF  IN  LOUISVILLE  ONITKRSITY. 


ttf)  JTour  !3jtg>U.|  HUTI'gUjMi^tlirrf  Illustrations. 
\ 
OF  THE 

UNIVERSITY 

O.         OF 
S^LiCViE 


FORTY-EIGHTH  EDITION. 

REWRITTEN  AND   ENLARGED. 


PHILADELPHIA: 

H.  C.  PECK  &  THEO.  BLISS. 
1860. 


In  preparation  by  Professor  Silliman, 

An  Elementary  Treatise  on  Natural  Philosophy,  for  Colleges 
and  Schools. 


Entered  according  to  the  Act  of  Congress,  in  the  year  1852,  by 
H.  G  PECK  &  TIIEO.  BLISS, 

in  the  Clerk's  Office  of  the  District  Court  of  the  Eastern  Pfotrict  ot 
I'eiinsylvani*. 


UTOIEOTYPED  BT  L.  JOHNSON  A*D  OOu 


PULXTED  BT  0.  SH£MUM. 


TO 


FOB  IWTY  YEARS  PROFESSOR  OF  CHEMISTRY  IN  YALE  COLLEOB, 


BB8IGNED   TO    PROMOTE   THAT  SCIENCE,    Tfl    WHICH   HE 

HAS   DEVOTED    HIS    LIFE, 
»   RESPECTFULLY  DEDICATED, 


THK  AUTHOR. 


^84529 


PREFACE  TO  THE  THIRD  REVISED  EDITION. 


DURING  the  five  years  -which  have  passed  since  the  second  edition  of 
this  work  was  prepared,  intense  activity  has  prevailed  in  all  depart- 
ments of  chemical  research.  Any  attempt  to  preserve  the  stereotype 
plates  of  that  edition  in  the  present  was  found  to  he  quite  impracti- 
cable. The  whole  work  has  been  entirely  revised,  rewritten,  and  so  far 
rearranged,  as  experience  has  shown  to  he  desirable.  Some  parts  have 
been  enlarged,  and  some  have  been  contracted,  so  that  on  the  whole  the 
size  of  the  volume  remains  much  as  before.  A  great  number  of  new 
illustrations  have  been  added,  more  than  doubling  the  number  in  the 
former  editions.  A  considerable  number  of  wood  cuts  have  been  taken 
fromKegnault's  excellent  Court  de  Chimie,  and  many  new  ones  have  been 
drawn  from  the  author's  apparatus.  Every  important  fact,  formula,  and 
number  in  the  work  has  been  carefully  compared  with  the  most  recent  and 
valued  authorities.  The  changes  made  in  the  atomic  weights  of  element- 
ary substances,  during  the  last  five  years,  have  been  numerous  and  im- 
portant; and  in  most  cases  these  changes  have  added  simplicity  to  the 
science.  The  new  facts  and  principles  gleaned  in  no  inconsiderable  num- 
bers for  this  edition,  have  been  woven  into  the  text  in  suc'a  a  manner  as 
to  present,  it  is  hoped,  an  uniformity  of  design. 

In  the  Organic  Chemistry,  greater  simplicity  and  unity  has  been 
giver.  U>  the  principles  involved  in  the  almost  unwieldy  mass  of  facts 
which  have  accumulated  so  rapidly  during  the  last  ten  years.  The 
author  has  again  to  acknowledge  his  obligations  to  his  friend  and  former 
associate,  Mr.  HUNT,  for  his  lucid  and  original  exposition  of  this  part  of 
the  subject. 

The  adoption  of  this  work  by  many  of  the  first  seminaries  of  learning 
in  this  country,  is  a  gratifying  evidence  to  the  author  that  his  design 
has  been  appreciated  ;  and  he  trusts  that  those  who  gave  their  confi- 
dence to  the  two  first  editions,  will  find  the  present  one,  in  many  import- 
ant respects,  superior  to  them. 


NEW  HAVEN,  September  30,  1852. 


FROM  THE  PREFACED  THE  FIRST  EDITION. 


THE  object  of  this  work  is  sufficiently  indicated  by  its  title.  It  hal 
grown  out  of  the  exigencies  of  teaching,  and  has  been  received  as  the 
text-book  in  the  public  lectures  at  Yale  College. 

It  is  important  that  a  work  of  this  kind  should  contain  only  such 
matter  as  is  actually  taught  to  a  class  by  recitations  and  lectures. 
All  fulness  beyond  this  is  unavailable  to  either  teacher  or  pupil,  and 
serves  often  to  embarrass  the  one  and  discourage  the  other.  This  is, 
perhaps,  the  reason  why  several  works,  otherwise  excellent,  have  failed 
to  answer  the  purpose  for  which  they  were  written.  The  science  of 
Chemistry  has  now  reached  the  point  where  its  first  principles  can  be 
presented  by  the  teacher  with  almost  mathematical  precision. 

Chemistry  has  attractions  of  an  economical  and  experimental  charac- 
ter, which  will  always  secure  for  it  a  place  in  every  system  of  educa- 
tion. Without  wishing  to  diminish  its  claims  to  attention  on  these 
grounds,  the  author  urges  the  paramount  advantages  possessed  by  his 
favourite  science,  as  a  study  peculiarly  fitted  to  train  the  mind  to  a  me- 
thodized and  logical  habit  of  thought.  If  nothing  more  is  to  be  derived 
from  its  study  than  the  entertainment  offered  by  brilliant  phenomena, 
and  a  knowledge  of  convenient  economical  processes,  the  pupil  will  fail 
of  its  most  important  advantage.  The  beautiful  philosophy,  the  perspi- 
cuous nomenclature,  and  lucid  method  of  modern  chemistry,  are  so  ob- 
vious that  they  cannot  fail  to  awaken  the  attention  of  every  intelligent 
pupil,  and  carry  him  on  his  course  of  intellectual  culture  with  rapid 
progress. 

The  author  has  consulted  all  tha  best  authorities  within  his  reach, 
both  in  the  standard  systems  of  England  and  France,  and  in  the  scien- 
tific journals  of  this  country  and  Europe.  The  works  of  Daniell,  Gra- 
ham, Brande,  Kane,  Fownes,  Gregory,  Faraday,  Mitscherlich,  Berzelius, 
Dumas,  Liebig,  and  Gerhardt,  have  all  been  used,  as  also  the  treatises 
of  Dr.  Hare  and  Prof.  Silliman. 

The  Organic  Chemistry  is  presented  mainly  in  the  order  of  Liebig  in 
his  Traite  de  Chimie  Organique.  The  author  takes  pleasure  in  ac- 
knowledging the  important  aid  derived  in  this  portion  of  the  work 
from  his  friend  and  professional  assistant,  Mr.  THOMAS  S.  HUNT,  whose 
familiarity  with  the  philosophy  and  details  of  Chemistry,  will  not  fail  to 
make  him  one  of  its  ablest  followers.  The  labour  of  compiling  the  Or- 
ganic Chemistry  has  fallen  almost  solely  upon  him. 

If  it  shall  be  found  to  meet  the  wants  of  both  teachers  and  pupils,  and 
to  promote  the  progress  of  Scientific  Chemistry  in  this  country,  the 
author  will  feel  that  he  has  not  laboured  in  vain. 

NEW  HAYEK,  December  30, 1846. 


TABLE  OF  CONTENTS. 


PART  I. 


PHYSICS. 


INTRODUCTION 

Sources   of  Natural   Know- 
ledge   13 

Observation 14 

Divisions  of  Natural  Science.  15 

MATTER. — General    Properties 

of  Matter 16 

Mechanical  Attraction 17 

Molecules 18 

Three  States  of  Matter— Co- 
hesion   19 

Capillary  Attraction 21 

Exosmose  and  Endosmose 23 

Mechanical  Properties  of  the 

Atmosphere 23 

Air-pumps 24 

Law  of  Mariotte 26 

Barometer 28 

Weight  of  Atmosphere 30 

Weight  and  Specific  Gravity  31 

Hydrometer 33 

CRYSTALLIZATION.— Nature  of 

Crystallization 36 

Polarity  of  Molecules 37 

Crystalline  Forms 38 

Measurement  of  Crystals 41 

LIGHT.— Sources  and  Nature...  43 

Undulations 44 

Properties  of  Light 46 

Reflection 47 

Simple  Refraction 48 

Analysis  of  Light 50 

Double  Refraction 52 

Polarization 53 

Chemical  Rays 55 

Phosphorescence 56 


HEAT.— Sources 57 

Properties 58 

Communication  of  Heat 59 

Radiation 60 

Conduction 61 

Vibrations 62 

Convection 65 

Transmission  of  Heat 66 

Expansion 69 

Thermometer 75 

Pyrometer 78 

Capacity  for  Heat 79 

Change  of  State  produced  by 

Heat 81 

Liquefaction,  Latent  Heat...  82 

Vaporization 85 

Boiling 86 

Spheroidal  State 87 

Boiling  in  vacuo 89 

Elevation   of  Boiling-points 

by  Pressure 90 

Steam  Engine 92 

Evaporation 93 

Density  of  Vapors 94 

Dew-point 95 

Hygrometers 96 

Diffusion    and    Effusion    of 

Gases 97 

Liquefaction  and  Solidifica- 
tion of  Gases 98 

ELECTRICITY 100 

Magnetic   Electricity,    Mag- 
netism    101 

Electrical  Machines 107 

Statical  Electricity 108 

Electroscopes 108 


CONTENTS. 


PAGE 

Theories  of  Electricity 110 

Leyden  Jar Ill 

Electrophorus 113 

Galvanism 114 

Voltaic  Pile 115 

Ohm's  Law 118 

Batteries 120 

Smee's  Battery 121 

Daniell's  Battery 122 

Grove's  Battery 123 

Bunsen's  Battery 124 

Electrical  Light 125 


PAfll 

Electro-Magnetism 127 

Amperes  Theory 128 

Electro-Magnets 130 

Electromagnetic  Telegraph..  131 
Prof.  Henry's  Discoveries....  134 

Magneto-Electricity 137 

Therm^Electricity 139 

Animal  Electricity 140 

Electrochemical  Decomposi- 
tions   142 

Faraday's  Researches 143 

Electrotype 148 


PART  II. 


CHEMICAL    PHILOSOPHY. 


ELEMENTS  AND  THEIR  LAWS  OP 

COMBINATION 150 

Table  of  Elementary  Bodies  152 

Laws  of  Combination 153 

Chemical  Nomenclature  and 
Symbols 155 


Combination  by  Volume 161 

Specific  Heat  of  Atoms 162 

Isomorphism  and  Dimorph- 
ism   162 

Chemical  Affinity 164 


PART  III. 


INORGANIC   CHEMISTRY. 


CLASSIFICATION  OF  ELEMENTS  169 

Oxygen 169 

Management  of  Gases 174 

Chlorine 176 

Compounds  of  Chlorine  with 

Oxygen 180 

Bromine 183 

Iodine 184 

Fluorine 186 

Sulphur 187 

Sulphurous  Acid 190 

Sulphuric  Acid 192 

Chlorids  of  Sulphur 187 


Selenium 198 

Tellurium 199 

Nitrogen 199 

The  Atmosphere 201 

Compounds  of  Oxygen  and 

Nitrogen 203 

Nitric  Acid 204 

Protoxyd  of  Nitrogen 206 

Nitric  Oxyd 208 

Phosphorus 210 

Compounds  of  Phosphorus 

with  Oxygen 213 

Carbon 216 


CONTENTS. 


9 


PA(JE 

Carbonic  Acid 220 

Carbonic  Oxyd 223 

Bisulphuret  of  Carbon 224 

Cyanogen 225 

Silicon 227 

Silica 228 

Fluorid  of  Silicon 229 

Boron 229 

Boracic  Acid 230 

Hydrogen 231 

Water 236 

Eudiometry 239 

Action  of  Platinum  with  Hy- 
drogen and  Oxygen 242 

Oxybydrogen  Blowpipe 244 

History  of  Water 246 

Peroxy d  of  Hydrogen 249 

Hydracids 250 

Chlorohydric  Acid 251 

Bromohydric  Acid 255 

lodohydrio  Acid 256 

Fluohydric  Acid 257 

Sulphydric  Acid 258 

Compounds  of  Hydrogen  with 

class  III 261 

Ammonia 262 

Phosphuretted  Hydrogen 265 

Compounds  of  Hydrogen  with 

the  Carbon  group 266 

Marsh  Gas 267 

Olefiant  Gas 268 

Combustion  and  Structure  of 

Flame 272 

Safety  Lamp 276 

METALLIC  ELEMENTS 

General  Properties  of  Metals  278 

Metallic  Veins 278 

Physical  Properties  of  Metals  280 
Chemical  Relations  of   the 

Metals 283 

Salts 285 

Potassium 288 

Compounds  of  Potassium 291 

Potash 292 

Salts  of  Potash 295 

Sodium 300 

Caustic  Soda,  Common  Salt..  301 

Sulphate  of  Soda 302 

Carbonate  of  Soda 304 

Nitrate  of  Soda 305 


PAGB 

Phosphates  of  St  da 306 

Borax 307 

Lithium 307 

Ammonium 308 

Compounds  of  Ammonium...  309 

Barium 311 

Strontium 313 

Calcium 314 

Gypsum 316 

Carbonate  of  Lime 317 

Magnesium 319 

Sulphate  of  Magnesia 320 

Aluminum 321 

Alums 322 

Silicates  of  Alumina 323 

Manufacture  of  Glass 323 

Pottery 327 

Glucinum,  Yttrium,  Zirco- 
nium, Thoria 328 

Manganese 328 

Iron 330 

Reduction  of. 334 

Chromium 336 

Nickel 339 

Cobalt 340 

Zinc 341 

Cadmium 342 

Lead 343 

Uranium 345 

Copper 345 

Vanadium,  Tungsten,  Colum- 
bium,  Titanium,  and  Mo- 
lybdenum   348 

Tin 349 

Bismuth 350 

Antimony 352 

Arsenic 354 

Detection  of  Arsenic  in  poi- 
soning   357 

Mercury 361 

Calomel 364 

Salts  of  Mercury 366 

Silver 366 

Cupellation 368 

Gold 371 

Palladium 372 

Platinum 373 

Iridium,  Osmium 375 

Rhodium,  Ruthenium 376 


10 


CONTENTS. 


PART  IV. 


ORGANIC   CHEMISTRY. 


PAGE 

INTRODUCTION 377 

Nature  of  Organic  Bodies....  377 
Laws    of    Chemical    Trans- 
formations   379 

Equivalent  Substitution 380 

Substitutions  by  residues 384 

Sesqui-salts,  Direct  Union...  385 
On  Combination  by  Volumes  386 

Density  of  Carbon  Vapor 386 

On  the  Law  of  the  Divisibility 

of  Formulas 387 

On  Isomerism 388 

On  Chemical  Homologues....  389 
Temperature  of  Ebullition...  390 
ANALYSIS   OP    ORGANIC    SUB- 
STANCES   390 

Density  of  Vapors 395 

Water 396 

Ammonia 397 

Carbonic  Acid 400 

SUGAR,  STARCH,  AND   ALLIED 

SUBSTANCES 401 

Cane,  Grape  Sugars 401 

Sugar  of  Milk,  Mannite 402 

Products  of  the  Decomposi- 
tion of  the  Sugars 403 

The  Vinous  Fermentation...  403 

Lactic  Acid 405 

Gum 407 

Starch 407 

Woody  Fibre 409 

Xyloidine,  Pyroxyline,  Guri- 

cotton 411 

Transformation     of    Woody 

Fibre 412 

Destructive    Distillation    of 

Wood 413 

Kreasote 413 

Wood-tar,  Paraffin,  Coal-tar  414 

Petroleum 415 

ALCOHOLS,  VINOL 415 

Action  of  Acids  upon  Alcohol  417 

Ethers 419 

Nitric,    Nitrous,     Perchloric 

Ethers 420 

Sulphovinic  Acid 420 

Silicic  Ethers,  Olefiant  Gas...  425 
Products  of  the  Oxydation  of 

Alcohol....  ..  426 


Chloral,  Sulphur  Aldehyd 428 

Acetic  Acid 429 

Acetates,  Acetate  of  Potash...  430 

Acetate  of  Lead 431 

Acetate  of  Copper,  Chlorace- 

ticAcid 432 

Acetic  Ether 433 

METHOL 434 

Wood-spirit,  Pyroxylio  Spi- 
rit, Methylio  Alcohol 434 

Sulphomethylic  Acid 435 

Oxydation  of  Methol 437 

AMYLOL,  Amylic  Alcohol 438 

Oxydation  of  Amylol 439 

Spermaceti,  Wax 440 

GLYCERIDS 441 

Soaps,  Butyric  Acid 442 

Phocenine,    Enanthylic   and 

Pelargonic  Acids 443 

Oleine,    Palmatine,    Marga- 
rine, Stearine 444 

Fatty  Acids 446 

ALKALOIDS  OP  ALCOHOL  SERIES  448 
Ethamine,  Methamine,  Amy- 

lamine 449 

Triethamine 450 

BITTER-ALMOND  OIL 452 

Benzoilol 452 

Chlorinized    Benzoilol,   Hy- 

drobenzamide 453 

Benzoic  Acid 454 

Benzen 455 

SALIC YLOL 458 

OTHER  ESSENTIAL  OILS 459 

Oil  of  Cinnamon 459 

Oil  of  Turpentine 459 

Oils  of  Juniper,  Pepper,  Ca- 
raway, Parsley,  <fec 460 

Camphor,  Borneo  Camphor...  461 

Resins 462 

Caoutchouc,  Gum-Elastic....  462 
Gutta  Percha 463 

VEGETAL  ACIDS 463 

Oxalic  Acid 464 

Tartaric  Acid 465 

Racernic  Acid,  Malic  Acid....  467 

Citric  Acid 469 

Tannic  Acid,  Tannin 469 

Gallic  Acid 470 


CONTENTS. 


11 


VEGETAL  ALKALOIDS 471 

Alkaloids  of  Cinchona 472 

Alkaloids  of  Opium 473 

Morphine,   Codeine,   Narco- 

tine ,..  474 

Strychnine,   Brucine,   Pipe- 

rine 475 

Theine,    Caffeine,    Theobro- 

mine,  Solanine 476 

Veratrine,  Aconitine,  Sangui- 
narine,  Emetine,  Nico- 
tine, Conine 477 

Amygdaline,  Emulsine 478 

Salicine,  Saligenine,  Salire- 

tine,  Helicine 479 

Populine,  Phloridzine 480 

Coloring  Matters 481 

Lecanorine 481 

Orcine,  Evernic  Acid,  Litmus  482 
Xanthine,  Alizarine,  Madder 

lake 483 

Carthamine,   Hematoxyline.  483 
Quercitrine,   Luteoline,  Mo- 

rine,  Chlorophyll 483 

Indigo 484 

Sulphindigotic  and  Sulpho- 
purpuric  Acids,  Saxon 

Blue 485 

Isatine,  Anthranilic  Acid 485 

THE  CYANIC  COMPOUNDS 486 

Hydrocyanic  Acid 486 

Cyanid  of  Potassium 488 

Cyanid  of  Ammonium 488 

Cyanogen 488 

Cyanates 489 

Urea 490 

Sulphocyanates 491 

Sulphocyanic  Acid 491 

Cyanoxsulphid,  Mellon 492 

Polycyanids 492 

Perchloric  Tricyanid,  Per- 
chloric Dicyanid,  Cya- 

nuric  Acid 493 

Melamine,  Ammelid,  Amme- 

line 494 

Fulminates 494 

Cyanethine 495 

Alanine,  Vinic  Urea 496 

Allophanic  Acid 496 

Trigenic  Acid 497 

Cyaniline,  Melaniline,  Cy- 
ameline,  Cyanharma- 
line !  ,..  497 


Ferrocyanids 498 

Yellow  Prussiate  of  Potash...  499 
Ferrocyanic  Acid,  Prussian 

Blue 500 

Ferricyanids,  Red  Prussiate 

of  Potash 500 

Nitroprussids 501 

Cobalticyanids 502 

Platinocyanids,  Argentocya- 

nid  of  Potassium 503 

Acids  of  the  Urine  and  Bile..  503 

Hippuric  Acid,  Glycoll 504 

Uric,  or  Lithic  Acid 505 

Allantoin,  Alloxan 506 

Alloxantine,  Dialuric  Acid...  507 

Uramile,  Murexid 508 

Parabanic  Acid, Amalic  Acid.  509 

Cholic,  Cholalic  Acids 509 

Choloidic  Acid,  Taurine,  Hy  o- 

cholalicAcid 510 

Biliary  Calculi 510 

NUTRITIVE    SUBSTANCES    CON- 
TAINING NITROGEN 511 

Protein,  Fibrin,  Albumin,  Ca- 
sein    511 

Gluten,  Vegetable  Albumin..  512 

Legumin 512 

Leucin,  Tyrosin 514 

Yeast... 516 

Gelatin 517 

THE  BLOOP 518 

Blood    Globules 518 

Hematosine 519 

Seroline 520 

Flesh  Fluid 522 

Creatine,  Creatinine 522 

Sarcosine,  Inosinic  Acid 523 

Saliva,  Pancreatic  Juice 523 

Gastric  Juice 524 

Pepsin,  Bile 524 

Chyle,  Urine 525 

Microcosmic  Salt 526 

Milk 527 

Eggs 528 

The  Brain  and  Nervous  Sub- 
stance   528 

Bones 529 

NUTRITION  OF  PLANTS  AND  OF 

ANIMALS , 530 

Food  of  Plants 531 

Manures 532 

Digestion 534 

Respiration 535 

Vital  Heat 537 


APPENDIX 539 


FIRST  PRINCIPLES 


OF 


CHEMISTRY. 


PART  I.— PHYSICS. 


INTRODUCTION. 

1.  OUR  knowledge  of  nature   begins   with   experience. 
While  this  teaches  us  that  like  causes,  under  similar  cir- 
cumstances, produce  like  effects,  we  recognise  also,  as  insepa- 
rable from  our  experience,  the  great  principle  that  every  event 
must  have  a  cause.     Man,  "  as  the  priest  and  interpreter  of 
nature,"  seeks  to   extend  his  experience   by   experiment. 
Every  experiment  is  but  a  question  addressed  to  nature,  ask- 
ing for  an  increase  of  knowledge ;  and  if  we  question  her 
aright,  we  may  be  sure  of  a  satisfactory  answer. 

2.  Observation  instructs  us  in  a  knowledge  of  the  external 
forms  of  nature,  and  we  thus  acquire  our  first  impressions  of 
the  various  departments  of  Natural  History.    Our  knowledge 
would,  however,  be  very  limited,  without  a  constant  effort 
to  extend  our  experience  by  experiment.     The  nations  of 
antiquity  excelled  greatly  in  many  branches  of  human  know- 
ledge, and  their  skill  in  the  arts  of  design  remains  unequalled. 
Their  ignorance,  however,  of  natural  phenomena,  and  the 
faws  by  which  they  are  governed,  was  remarkable ;  because 
they  overlooked  the  true  connection  between  cause  and  effect. 


1.  What  is  the  beginning  of  our  knowledge  of  nature  ?  What  great 
principle  do  we  recognise  in  connection  with  experience  ?  What  is  au 
experiment?  2.  What  does  observation  teach?  How  does  it  extend  oui 
knowledge  ? 

18 

184529 


14  INTRODUCTION. 

The  ancient  philosophy  abounded  in  plausible  arguments 
regarding  those  natural  phenomena  which  could  not  fail  to 
arrest  the  attention  of  an  intelligent  people  ;  but  its  reason- 
ings were  based  on  an  d  priori  assumption  of  a  cause,  and 
not  upon  an  inductive  inquiry  after  facts  and  their  connec- 
tions. It  failed  to  apply  iteelf  to  the  careful  collection  and 
study  of  facts  in  order  to  science.  Facts  in  nature  are  th& 
expression  of  the  Divine  will  in  the  government  of  the  phy- 
sical world.  The  universe  of  matter  is  made  up  of  facts, 
which,  observed,  traced  out,  and  arranged,  lead  us  to  the 
knowledge  of  certain  laws  and  forces  which  proceed  directly 
from  the  mind  of  God.  These  are  the  "  laws  of  nature  :" 
science  is  but  the  exposition  of  them  and  of  science  based 
upon  such  grounds,  the  ancient  philosophy  was  completely 
ignorant. 

3.  It  is  important  to  distinguish  that  knowledge  which  is 
purely  intellectual  in  its  character,  from  that  which  results 
from  observation  and  experience.    Speaking  of  this  subject, 
one  of  the  most  learned  of  living  philosophers  remarks :  "A 
clever  man,  shut  up  alone,  and  allowed  unlimited  time,  might 
reason  out  for  himself  all  the  truths  of  mathematics,  by  pro- 
ceeding from  those  simple  notions  of  space  and  number,  of 
which  he  cannot  divest  himself  without  ceasing  to  think ;  but 
he  could  never  tell,  by  any  effort  of  reasoning,  what  would 
become  of  a  lump  of  sugar  if  immersed  in  water,  or  what 
impression  would  be  produced  on  the  eye  by  mixing  the 
colors  yellow  and  blue." — (Herschel.)     We  may,  however, 
with  propriety  doubt,  whetner  there  is  any  knowledge  or 
philosophy  so  purely  intellectual,  or  absolute,  that  it  does 
not  imply  some  previous  recognition  of  physical  facts. 

4.  The  observation  of  facts  forms  only  the  foundation  of 
science, — an  isolated  fact  has  no  scientific  value.    The  know- 
ledge of  physical  laws  deduced  from  the  study  of  observed 
facts  will  enable  the  philosopher  to  foretell  the  result  of  the 
possible  combination  of  those  laws,  and  to  assign  reasons  for 
apparent  departures  from  them.     In  this  way  discoveries  are 
predicted  and  detailed ;  observation  is  anticipated,  and  called 


Characterize  the  ancient  philosophy.  How  did  it  fail?  What  are 
facts  ?  What  are  laws  of  nature  ?  What  is  science  ?  3.  What  convenient 
dirtinction  is  named?  What  remark  is  quoted  in  illustration  of  this? 
4.  What  is  said  of  observation?  What  of  an  isolated  fact?  What 
does  a  knowledge  of  natural  laws  enable  the  philosopher  to  do  ? 


INTRODUCTION.  15 

on  to  verify  the  alleged  discovery.  The  perturbations  of  the 
planet  Uranus  indicated  the  existence  of  some  body  in  space 
heretofore  unknown.  When  Le  Verrier  had  reconciled  these 
disturbances  with  the  supposed  influence  of  a  new  planet, 
and  determined  its  elements  of  motion,  he  had  as  truly  dis- 
covered the  remote  sphere,  as  when  the  German  astronomer, 
by  pointing  his  telescope  to  the  precise  place  in  the  heavens 
which  Le  Verrier  had  designated,  announced  to  the  world 
that  the  stupendous  prediction  was  verified  by  observation. 
In  like  manner,  a  familiarity  with  chemical  laws  enables  the 
chemist  to  foretell  the  result  of  combinations  which  he  has 
never  investigated,  and  in  some  cases  to  assign  with  confi- 
dence the  constitution  of  bodies  which  he  has  never  ana- 
lyzed. 

5.  Our  knowledge  of  Natural  Science  is  conveniently 
classified  under  the  three  great  divisions  of  Natural  History, 
Physical  Philosophy,  and  Chemistry.  The  first  teaches  us 
the  characters  and  arrangement  of  the  various  forms  of  ani- 
mal and  vegetable  life  and  minerals,  giving  origin  to  the 
sciences  of  Zoology,  Botany,  and  Mineralogy.  Physical 
Philosophy  explains  the  forces  by  which  masses  of  matter 
are  governed,  and  unfolds  the  laws  of  Light,  of  Electricity, 
and  of  Heat. 

Chemistry  teaches  us  the  intimate  and  invisible  constitu- 
tion of  bodies,  and  makes  known  the  compounds  which  may 
be  formed  by  the  union  of  simple  substances,  the  laws 
of  their  combination,  and  the  properties  of  the  new  com- 
pounds. It  investigates  the  forces  resident  in  matter,  and 
which  are  inseparable  from  our  idea  of  molecular  action, — 
forces  whose  play  produces  the  phenomena  of  Light,  of 
Heat,  and  of  Electricity.  Chemistry  also  unfolds  the  won- 
derful operations  of  animal  and  vegetable  life,  so  far  as  their 
functions  depend  upon  chemical  laws,  as  in  the  processes  of 
respiration  and  digestion,  giving  the  special  department  of 
Physiological  Chemistry. 


Illustrate  this  in  case  of  the  perturbations  of  Uranus.  5.  How  is  our 
knowledge  of  nature  classified?  What  does  the  first  teach?  Physical 
philosophy  teaches  what  ?  Define  the  province  of  Chemistry. 


16  MATTER. 

I.  MATTER. 

General  Properties  of  Matter. 

6.  Experience,  founded  on  the  evidence  of  our  senses,  con- 
vinces us  of  the  existence  of  matter.   "We  feel  the  resistance 
which  it  offers  to  our  touch ;  we  see  that  it  has  form,  and 
occupies  space,  and  hence  we  say  it  has  extent ;  and,  lastly, 
we  attempt  to  raise  it,  and  we  find  ourselves  opposed  by  a 
certain  force  which  we  call  weight. 

Matter  possesses  extension,  because  it  occupies  some  space. 
It  is  impenetrable,  because  one  particle  of  matter  cannot 
occupy  the  same  space  with  another  at  the  same  time.  It 
has  gravity,  because  it  obeys  the  law  of  universal  attraction. 
Whatever,  therefore,  possesses  these  three  qualities,  is 
matter. 

7.  All  the  changes  of  which  matter  is  capable  may  be 
referred  to  one  of  three  great  principles  or  forces,  and  to 
their  modifications  or  combinations.   These  are  ATTRACTION, 
REPULSION,  and  VITALITY. 

Attraction  is  divided  into  Mechanical  and  Chemical. 

8.  Mechanical  Attraction  is  divided  into,  1.  Gravitation, 
acting  at  all  distances,  and  between  all  masses.     2.  Cohesion, 
acting  between  bodies  or  particles  of  the  same  kind  only, 
and  at  immeasurably  small  distances.     To  this  power  are 
referred  all  the  phenomena  of  solidification  and  crystalliza- 
tion.    3.  Adhesion,  acting  between  bodies  of  unlike  kinds, 
at  immeasurably  small  distances,  and  forming  mixed  masses. 
Chemical  Attraction,  or  Affinity,  exists  only  between  mole- 
cules or  particles  of  unlike  kinds,  acts  only  at  immeasurably 
small  distances,  and  produces  homogeneous  masses  which 
have  properties  unlike  the  constituent  elements.     In  a  word, 
gravity  acts  on  all  matter  and  at  all  distances.     Cohesion 
acts  only  on  the  same  kind  of  matter  at  insensible  distances. 
Chemical  affinity  acts  only  between  unlike  particles  at  in- 
sensible distances. 

Repulsion  is  a  force  seen  in  the  impenetrability  of  matteJ 


6.  "Whence  our  knowledge  of  matter  ?  Define  its  properties.  7.  Name 
three  forces  governing  matter.  8.  Subdivide  mechanical  attraction. 
How  is  chemical  distinguished  from  mechanical  attraction?  What  of 
repulsion  ?  Define  vitality. 


OF   MECHANICAL  ATTRACTION.  17 

and  in  its  power  of  expansion.  It  is  the  antagonist  of  co- 
hesion, or,  as  it  is  sometimes  called,  the  attraction  of  aggrega- 
tion. Heat  resolves  the  several  forms  of  mechanical  attrac- 
tion, and  surrenders  matter  to  the  dominion  of  repulsive  force, 
by  which  its  particles  or  molecules  are  widely  separated. 

Vitality  rules  superior  to  all  the  laws  of  mechanical  and 
of  chemical  attraction,  suspending,  modifying,  or  applying 
them  for  the  production  of  those  complicated  results  which 
are  seen  in  the  organized  structures  of  plants  and  animals. 

9.  Such  are  the  great  forces  to  which  matter  is  subject. 
All  the  changes  resulting  from  the  operation  of  the  forms 
of  mechanical  attraction  belong  to  Physics.    Those  referable 
to  vitality  fall  within  the  province  of  the  physiologist. 

The  consideration  of  the  changes  produced  in  matter  by 
the  exertion  of  affinity,  or  chemical  attraction,  constitutes 
the  appropriate  business  of  the  chemist. 

All  that  relates  therefore  to  physics  might  be  properly 
dismissed  from  a  manual  of  chemistry ;  but  it  is  usual  for 
the  chemical  student  to  devote  a  share  of  his  attention  to 
those  departments  of  physics,  some  knowledge  of  which  i$, 
essential  to  a  correct  understanding  of  chemical  phenomena.^ 

Of  Mechanical  Attraction. 

10.  Gravitation  is  a  force  measured  in  any  particular  case 
by  weight,  whether  we  speak  of  a  movable  mass  capable  of 
equipoise  in  our  balances  or  of  the  weight  of  the  planets  as 
deduced  from  their  observed  motions.     It  acts  at  all  dis- 
tances upon  all  matter,  and  is  directly  as  the  mass  and  in- 
versely as  the  square  of  the  distance.    The  weight  of  a  body 
is  therefore  proportioned  to  the  number  of  molecules  or  par- 
ticles which  it  contains. 

11.  Cohesion,  is  seen  alike  in  solids,  in  fluids,  and  in 
gases — three  states  of  matter  incident  to  the  equilibrium  of 
the  forces  of  repulsion  and  cohesion,  and  modified  by  the 
laws  of  heat.    Those  who  regard  light,  heat,  electricity,  and 
magnetism  as  imponderable  bodies,  refer  their  properties 
also  to  the  antagonistic  power  of  repulsion,  by  which  these 
manifestations  are  so  controlled  that  we  have  no  proof  of 
the  existence  of  mutual  cohesion  among  their  particles. 


9.  What  does  physics  include?     10.  How  is  Gravitation  measured f 
Define  its  law.    11.  What  of  Cohesion  ? 


18  MATTER. 

In  the  force  of  cohesion,  or  attraction  of  aggregation,  as 
manifest  in  solid  bodies,  we  recognise  a  power  which  opposes 
the  division  of  matter. 

12.  Divisibility  of  matter. — The  question  of  the  infinite 
divisibility  of  matter  has  in  past  times  been  the  subject  of 
most  animated  discussions,  and  until  the  discoveries  of  modern 
chemistry,  no  satisfactory  solution  was  reached.     We  know 
that  the  largest  and  most  solid  masses  of  matter,  even  en- 
tire mountains,  may  be  ground  down  by  mechanical  force  to 
dust  so  fine  that  the  winds  will  bear  it  away,  but  each  mi- 
nute particle  still  occupies  some  space;  and  we  may  imagine 
that  a  great  multitude  of  smaller  particles  may  be  formed 
from  its  further  division.     A  grain  of  gold  may  be  spread 
out  so  thin  as  to  cover  600  square  inches  of  surface  on  silver 
wire,  and  one  ounce,  in  this  manner,  be  made  to  cover  1300 
miles  of  such  wire.     One  grain  of  green  vitriol,  (sulphate 
of  iron,)  dissolved  and  diffused  in  20  million  grains  of  water, 
will  still  be  easily  detected  by  the  proper  tests.    The  delicate 
perfume  of  musk  and  the  aroma  of  flowers  are  remarkable 
examples  of  minute  division  in  matter. 

The  organic  world  also  presents  us  with  beautiful  ex- 
amples of  the  great  divisibility  of  matter,  in  the  remarkable 
forms  of  animalcules  revealed  by  the  microscope,  many 
millions  of  which  can  be  embraced  in  a  single  drop  of  water. 
Yet  each  of  these  inconceivably  minute  organisms  has  its 
own  muscular,  digestive,  and  circulatory  systems.  How  mi- 
nute, then,  the  ultimate  particles,  of  which  many  myriads 
must  be  contained  in  each  animalcule  ! 

Chemistry  has  happily  resolved  the  question  of  infinite 
divisibility,  by  proving  that  all  matter  consists  of  certain 
particles  of  definite  values,  whose  relative  weights  and  bulks 
may  be  precisely  determined.  These  particles  are  called — 

13.  Mokcules*  or  Atoms. — Ultimate  chemical  analysis 
has   demonstrated  that   matter   consists    of  many  distinct 
varieties,  called   elementary    or    simple    bodies,    and   that 


12,  What  degree  of  divisibility  exists  in  matter?     Give  some  illustra- 
tions.    13.  What  is  said  of  molecules? 


*  Molecule,  a  diminutive  of  moles,  a  mass.  This  term  is  preferable  to 
'atom'  or  'ultimate  particle,'  as  implying  no  theory,  which  both  the  others 
do.  Atom  is  from  a,  privative,  and  temno,  I  cut,  signifying  their  supposed 
indivisibility. 


THE    THREE   STATES   OP   MATTER.  19 

these  several  separate  sorts  of  matter  possess  each  its 
own  combining  quantity,  from  which  it  never  varies,  and 
this  quantity,  called  its  equivalent,  atomic,  proportional,  or 
combining  number,  is  susceptible  of  accurate  determination 
by  the  balance.  The  molecules  of  simple  bodies  are  neces- 
sarily simple  themselves,  while  the  molecules  of  compound 
bodies  are,  on  the  contrary,  complex.  Whatever  size  these 
molecules  may  possess,  they  are  the  centres  of  all  the 
forces  and  qualities  whose  united  effects  and  activity  give 
matter  its  physical  or  chemical  properties.  Although  we 
may  never  know  the  absolute  weight  of  any  molecule,  we  do 
know  with  much  certainty  the  relative  size  and  weight  of 
the  molecules  of  over  sixty  sorts  of  simple  matter,  which  che- 
mistry has  revealed  to  us.  The  laws  of  crystallogeny  also 
inform  us  that  these  molecules  have  an  inherent  difference 
of  form;  some  being  spherical,  while  others  are  ellipsoidal. 

Of  Cohesion  in  reference  to  the  three  states  of  Matter, 
the  Solid,  the  Liquid,  and  the  Gaseous. 

14.  Properties  of  Solids. — It  is  a  distinguishing  pro- 
perty of  solids  to  have  their  particles  bound  together  by  so 
strong  an  attraction  as  in  a  great  measure  to  destroy  their 
power  of  moving  among  each  other. 

No  solid,  however,  not  even  gold  and  platinum,  which 
are  the  most  compact  solids  known,  has  its  particles  of  mat- 
ter so  aggregated  as  to  be  incapable  of  some  condensation. 
Blows,  pressure,  or  a  reduction  of  temperature,  will  condense 
almost  all  solids  into  a  smaller  bulk.  Water  may  even  be 
forced  through  the  pores  of  gold,  by  very  great  mechanical 
pressure.  All  solid  bodies  are,  therefore,  considered  as  por- 
ous, and  their  particles  are  believed  to  touch  each  other  in 
comparatively  few  points. 

Cohesion  in  solids  may  be  destroyed  either  by  mechanical 
violence,  as  in  pulverization ;  by  solution,  as  in  the  case  of 
saline  bodies  soluble  in  water;  or  by  the  agency  of  heat,  as 
in  the  fusion  of  wax  or  lead.  The  mobility  of  the  particles 
in  solid  bodies  is  shown  also  in  the  elasticity,  malleability, 
ductility,  and  laminability  of  many  metals,  which  are  among 
their  most  useful  properties.  Hardness  is  a  quality  having 

What  forms  have  the  molecules  ?  14.  What  mobility  have  particles  in 
solids  ?  What  of  pores  in  solids?  How  may  cohesion  be  destroyed?  *; 


•20 


MATTER. 


no  relation  to  the  preceding,  and  is  possessed  by  solids  in  very 
various  degrees,  and  apparently  without  reference  either 
to  the  density  or  chemical  nature  of  the  substances, — for 
gold  and  platinum,  among  the  heaviest  of  known  bodies,  are 
comparatively  soft,  while  the  diamond,  which  is  only  about 
one-sixth  part  as  heavy  as  these  metals,  is  the  hardest  of  all 
known  substances.  Cohesive  attraction,  when  once  disturbed 
by  mechanical  violence,  is  not  usually  brought  into  exercise 
again  by  mere  approach  of  the  separated  particles.  The 
broken  fragments  of  a  glass  vessel  or  portion  of  stone  do  not 
reunite  at  ordinary  temperatures.  Nevertheless,  we  have 
some  examples  of  a  contrary  nature. 

If  we  press  together 
two  smooth  surfaces  of 
lead,  clean  and  bright, 
as,  for  example,  the 
halves  of  a  leaden 
sphere,  (fig.  1,)  cut 
through,  they  will  ad- 
here or  unite  together 
so  firmly  as  to  require 
the  power  of  several 
pounds  weight  to  draw 
them  asunder,  as  shown 
in  the  annexed  figure. 
The  plates  of  polished 
glass,  also,  which  are 
prepared  for  large  mir- 
rors, if  allowed  to  rest 
together  with  their  sur- 
faces in  close  contact, 
have  been  known  to 
unite  so  firmly  as  to 
break  before  they  would  yield  to  any  effort  to  separate  them. 
In  these  cases,  actual  contact  of  contiguous  particles  is  ef- 
fected, and  thus  the  conditions  of  cohesive  attraction  are 
fulfilled.  We  may  regard  the  welding  of  iron  and  the  cohe- 
sion of  masses  of  dough  or  putty  as  examples  of  a  similar 
kind.  The  casting  of  metals  by  voltaic  electricity,  from  cold 
solutions  of  their  salts,  also  affords  us  elegant  examples  of 
adhesive  attraction. 


What  of  hardness  ?  Give  examples  of  cohesion  at  common  temperature!. 


THE   THREE   STATES   OP   MATTER. 


21 


15.  In  fluids,  the  particles  have  perfect  freedom  of  mo- 
tion among  themselves.  They  are  either  inelastic  liquids, 
like  water,  or  elastic  gases  or  vapours,  like  air  and  steam. 
A  gas  is  a  permanent  elastic  fluid  :  a  vapour  is  such  only  in 
certain  conditions  of  temperature  and  pres- 
sure. In  water  we  have  a  familar  example  of 
a  body,  presenting  the  three  conditions  of  mat- 
ter, in  the  ordinary  changes  of  the  seasons. 

Liquids  are  not  completely  inelastic,  but 
are  compressible  to  a  very  slight  extent  by 
pressure,  as  is  shown  in  the  apparatus  of 
Oersted,  fig.  2.  A  small  glass  bulb  &,  with 
a  narrow  neck,  is  filled  with  water  lately 
boiled,  and  placed  in  the  glass  vessel  a,  also 
filled  with  water  by  the  funnel  g-}  a  metallic 
plug  h  is  forced  down  by  the  screw  7c,  pro- 
ducing any  required  pressure.  A  small  glo- 
bule of  mercury  in  the  stem  of  b  by  its  de- 
scent notes  the  amount  of  condensation  which 
the  water  in  b  suffers.  No  change  of  dimen- 
sions in  the  glass  b  can  happen,  because  it  is 
equally  compressed  from  within  and  without. 
In  this  way  the  compressibility  of  water  has 
been  shown  to  be  equal  to  one  part  in  22,000 
for  each  atmosphere  of  15  pounds  pressure. 
Alcohol  has  about  half  this  degree  of  compres- 
sibility; ether  about  one-third  more,  and 
mercury  only  about  one-twentieth  as  much. 

16.  Capillary  attraction  is  a  form  of  cohesion  seen  in 
liquids.  If  a  tube  with  a  very  fine  bore,  and  open  at  both 
ends,  is  immersed  in  water,  it  will  be  observed  that  the 


Fig.  2. 


liquid  rises,  as  seen  in  fig.  3,  to  a  certain 
elevation  in  the  tube,  and  to  a  less  degree 
also  on  the  outer  surface.    In  mercury,  (fig. 
4,)  on  the  contrary,  which  does  not  moisten 
the  glass,  there  is  a  depression  of  the  column 
in  the  tube,  and  the  surfaces  of  the  mercury 
are  convex.     The  height  to  which  a  fluid 

•11*          *               j      i         l                    •  1  1        •  •        •        •                      i 

I 

~ 

1 

Fig.  3.    Fig.  4. 

will  rise  in  a  tube  by  capillarity  is  inversely  as  the  diameter 


15.  How  are  the  particles  in  fluids?  Are  fluids  elastic?  Illustrate  it 
by  the  case  of  water?  16.  What  is  capillarity?  What  relation  has  dia- 
meter to  capillarity? 


MATTER. 


of  the  tube.  Two  plates  of  glass  held  as  in  fig.  5,  opening 
like  the  leaves  of  a  book,  and  their  lowei 
edges  immersed  in  a  fluid,  show  this  law 
by  the  curve  which  the  liquid  assumes. 
By  the  power  of  capillary  attraction,  tho 
wick  supplies  fuel  to  the  lamp  or  candle. 
Plugs  of  dry  wood  driven  into  holes  bored 
in  granite,  and  then  saturated  with  water, 
swell  so  much  by  the  water  taken  into  their 
pores  by  capillarity  that  the  rocks  are  split 
open .  Even  a  bar  of  lead  or  tin,  bent  like  the 
letter  U  and  placed  by  one  end  in  a  vessel 


Fig.  5. 


of  mercury,  will,  after  some  time,  convey  it  out  of  the  vessel 
drop  by  drop.  Two  small  balls,  one  of  wax  and  one  of  cork, 
^  (fig.  6,)  thrown  upon  the  surface  of 

JB »_  water,  manifest  repulsion  at  first, 

for  the  water  not  wetting  the  wax 
while  it  does  the  cork,  causes  an 
Fis-  6'  elevation    about   the    latter,  from 

which  the  former,  so  to  speak,  rolls  off,  and  the  balls  sepa- 
rate in  the  direction  of  the  arrows.  Two  balls  of  cork,  for  a 
like  reason,  attract  one  another.  Hence  the  familiar  fact 
that  chips  on  the  surface  of  quiet  water  always  crowd  to- 
gether, and  gather  about  a  log  or  larger  body  on  the  surface. 
The  wetting  of  surfaces  by  a  fluid  is  perhaps  a  sort  of  chemi- 
cal affinity.  Iron,  glass,  the  skin,  or  a  piece  of  wood  are 
not  wet  by  mercury;  while  gold,  silver,  lead,  and  many 
other  metals  are  so.  Oil  spreads  itself  in  a  thin  film  on  the 
surface  of  water,  and  by  its  cohesion  quiets  the  agitation  of 
moderate  waves. 

17.  The  cohesion  in  liquids  is  much  greater  than  is  com- 
monly imagined.      A  disc  of  glass   suspended   from    the 
beam  of  a  balance  over  a  surface  of  water  will  adhere  with 
a  measurable  force  to  the  water  when  brought 
in  contact  with  it.    The  force  required  to  with- 
draw it  is  that  which  will  rupture  the  cohe- 
sion of  the  outer  row  of  particles  at  the  edge  of 
the  disc,  then  the  next  row,  and  so  on  to  the 
centre  a,  as  shown  in  the  circles  on  fig.  7.     In 
Fig.  7.        the  soap-bubble  we  see  a  thin  film  of  water, 

Illustrate  this  by  fig.  5.  Explain  the  action  of  light  bodies  on  water. 
What  is  wettiiig?  17.  What  of  cohesion  in  liquids?  Explain  the  adhe- 
sive disc  and  the  soap-bubble. 


THE    ATMOSPHERE. 


23 


giving  us  a  beautiful  example  of  the  cohesive  power  of  water. 
It  is  a  great  hollow  drop  of  water.  The  cohesive  power 
in  the  film  of  the  bubble  is  so  great  that  if  the  pipe  be 
taken  from  the  mouth  before  the  bubble  leaves  it,  a  stream 
of  air  will  be  forcibly  driven  from  the  bore  by  the  contrac- 
tion of  the  film,  which  will  deflect  the  flame  of  a  candle.  To 
the  same  cause  is  ascribed  the  spherical  form  of  the  dew- 
drop,  the  cohesion  in  the  outer  row  of  particles. 

18.  In  the  structure  of  plants  and  of  animals,  capillary 
attraction  performs  functions  of  the  highest  importance  in 
the  economy  of  life.     Animal  membranes  possess  the  power 
of  exuding  or  of  absorbing  fluids  from  their  surfaces.     This 
power  has  by  several  authors  been  considered  as  a  special 
attribute  of  animal  tissues,  and  as  such  has  received  the 
name  of  endosmosc  and  exosmose,  or  the  inward  and  the  out- 
ward  force  of   membranes.     These   actions  are    generally 
regarded  as  modifications  of  capillarity,  and  may  be  well 
illustrated  by  the  endosmometer,  (fig.  8.)     An 

open  glass  b  has  it  lower  end  tied  over  by  a  bit 
of  bladder  c,  and  its  upper  opening  elongated 
by  a  narrow  glass  tube  a,  this  apparatus  is 
filled  with  weak  sugar-water,  and  is  placed  in 
an  outer  vessel  n,  filled  with  strong  syrup  of 
sugar.  Soon  the  column  of  fluid  is  seen  to 
mount  from  a  to  o  or  out  at  the  top,  from  the 
penetration  of  the  denser  fluid  through  the 
membrane.  The  power  which  plants  possess  of 
absorbing  the  nutritive  fluids  from  the  soil 
through  the  delicate  bulbous  ends  of  their  spog- 
nioles  is  supposed  to  be  identical  with  that  force 
shown  in  this  instrument. 

19.  In  gases,  the  force  of  cohesion  among  the  particles 
is  entirely  subordinate  to  the  repulsive  action  by  which  they 
are  expanded.     The  physical  properties  of  gaseous  bodies 
are  best  understood  when  we  study 

* 
TJie  Mechanical  Properties  of  the  Atmosphere. 

20.  We  on  the  surface  of  this  earth  are  at  the  bottom 
of  a  vast  aerial  ocean,  in  which  we  live  and  move  and  have 


Fig. 


Whence  the  form  of  the  dew-drop?     18.  What  is  endosmose?    What 
exosmose?    Explain  the  endosinometer.    19.  What  of  cohesion  in  gases  ? 


24 


MATTER.. 


our  being.  From  its  chemical  influence  we  cannot  escape, 
nor  free  ourselves  from  the  vast  load  of  its  mechanical  pres- 
sure which  we  unconsciously  sustain.  It  penetrates  deeply 
into  the  crust  of  the  earth,  and  is  largely  dissolved  in  its 
waters.  All  that  relates  to  its  chemical  history  will  he 
given  in  its  appropriate  place.  Its  mechanical  properties 
demand  attention  now.  What  is  true  of  the  mechanical 
properties  of  air  is  also  true  of  the  gases. 

21.  Elasticity. — Vessels   filled    only   with  air  we   call 
empty ;  but  it  is  obvious,  when  we  plunge  an  empty  air-jar 
beneath  the  surface  of  water,  that  it  contains  an  elastic  and 
resisting  medium,  which  must  be  displaced  before  the  vessel 
can  be  filled  with  water.     Elasticity  is  the  most  remarkable 
physical  property  of  the  atmosphere  and  of  all  gases.     Upon 
this  property  depends  the  construction  of 

22.  The  air-pump,  an  instrument  in  principle  like  the 
common  water-pump.     It  depends  for  its  action  on  the  elas- 
ticity of  the  air.     Suppose  two  tight-bottomed  cylinders,  a 
and  b,  (fig.  9,)  to  be  filled  with  air.     If  a  solid  plug,  or  pis- 
ton, is  fitted  to  each  so  tightly  that  no  air  can  pass  between 

it  and  the  sides  of  the  vessel,  we 
shall  find  it  impossible  to  force  down 
the  piston  to  the  bottom  of  the  cylin- 
der. It  descends  a  certain  distance 
with  an  increasing  resistance,  and 
is  again  restored,  as  with  the  force  of 
a  spring,  so  soon  as  the  pressure  is 
removed.  If  we  suppose  one  of  the 
pistons  to  be  in  the  position  shown  in 
b,  and  the  air  beneath  it  of  the  same 
tension  or  density  as  that  above,  and 
we  attempt  to  draw  out  the  plug  by 
its  stem,  we  also  feel  a  continually 
increasing  resistance,  and  the  piston 
Fig-  9.  returns  forcibly  to  its  former  posi- 

tion when  we  release  our  hold.  We  thus  demoistrate  the 
elasticity  of  the  air,  and  also  its  weight  and  pressure.  Such 
an  arrangement  of  apparatus,  slightly  modified,  is  an  air- 
pump.  If  each  of  the  pistons  is  pierced  with  a  hole,  over 


20.  What  is  said  of  the  aerial  ocean?  21.  Demonstrate  the  elasticity  of 
air  by  an  empty  vessel.  21.  What  is  the  air-pump?  How  does  it  eui 
ploy  elasticity  ?  Illustrate  this  by  tig.  9. 


THE    ATMOSPHERE. 


25 


10. 


which  is  a  flap,  or  valve,  of  leather  or  silk  v,  opening  upward, 
and  closing  with  the  slightest  downward  pressure,  and  a 
similar  opening,  or  valve, 
be  provided  in  the  bottom 
of  each  cylinder  v,  we  have 
an  air-pump.  (Fig.  10.) 
It  remains  only  to  connect 
the  cylinders  by  a  duct 
with  the  plate  on  which 
the  air-receiver  R  is  placed, 
and  to  provide  suitable 
movements  for  the  pistons 
by  a  lever  or  otherwise, 
and  our  instrument  is 
complete.  The  plate  and 
receiver  are  accurately 
ground  to  fit  air-tight,  and 
great  pains  are  taken  to 
have  all  parts  of  the  ap- 
paratus as  perfectly  air-tight  as  possible. 

23.  Vacuum. — It  is  obvious  that  the  air  in  the  receiver  will, 
by  virtue  of  its  elasticity,  rush  into  the  cylinders  alternately 
as  these  are  moved;  the  valves  in  the  cylinders  preventing 
the  return  of  the  air  to  the  receiver,  while  they  permit  the 
escape  of  the  successive  portions /rom  within,  and  those  on 
the  piston  closing  the  access  of  the  outer  air.  Thus,  with 
each  movement  of  the  lever,  fresh  portions  of  air  from  the 
receiver,  more  and  more  rare  each  time,  will  find  their  way  to 
the  cylinders  arid  be  pumped  out,  while  the  space  in  R  be- 
comes constantly  more  void,  until  the  vacuum  is  completed. 
This  happens  whenever  the  weight  and  resistance  of  the 
valves  in  the  cylinders  is  greater  than  the  elastic  force  of  the 
rarefied  air  in  the  receiver.  And  hence  it  is  obviously  impos- 
sible to  make  ^perfect  vacuum  by  mechanical  means.  There 
will  always  remain  a  certain  very  tenuous  atmosphere  in 
even  the  most  perfect  and  delicate  air-pump,  unless,  indeed, 
it  be  removed  by  chemical  means.  This  may  be  done  by  em- 
ploying a  bell-jar  filled  with  carbonic  acid,  the  last  portions 
of  which  may  be  removed  by  potassa  or  caustic  lime — pre- 


How  are  the  valves  of  the  pump  arranged?  23.  What  is  a  vacuum? 
Why  is  a  perfect  vacuum  impossible  ?  How  ma\  the  last  portions  of  air 
be  removed? 


26 


MATTER. 


I 


viously  placed  for  that  purpose  in  a  vessel  on  the  pump- 
plate.  The  French  instruments  often  have  the  cylinders  of 
glass,  to  expose  the  mechanical  movements 
of  the  valves  and  pistons.  Excellent  air- 
pumps,  with  only  one  cylinder,  on  the  plan 
proposed  by  Leslie,  are  furnished  by  the  in- 
strument-makers in  Boston  and  New  York. 
24.  The  bulk  and  density  of  the  atmosphere 
varies  with  the  mechanical  pressure  to  which 
it  is  submitted.  This  inference  is  drawn 
from  what  has  just  been  said  regarding  the 
theory  of  the  air-pump.  The  volume  of  the 
air  is  inversely  as  the  pressure  to  which  it 
is  subjected,  while  its  density  is  directly  as 
this  pressure.  This  is  known  as  Mariotte's 
law,  from  its  discoverer,  an  Italian  philoso- 
pher of  that  name. 

Fig.  11  shows  the  simple  apparatus  used 
for  demonstrating  this  law.  It  is  a  glass  tube 
turned  up  and  sealed  at  the  lower  end  :  a  gra- 
duated scale  of  equal  parts  is  attached  to  it. 
Mercury  is  poured  into  the  open  end  of  this 
tube  so  as  to  rise  just  to  the  first  horizontal 
line;  a  portion  of  air  of  the  ordinary  elas- 
ticity is  thus  enclosed  in  the  short  limb  of 
9  inches.  Now  if  mercury  be  poured  into 
the  longer  leg,  so  that  it  may  stand  at  30 
inches  above  the  level  of  the  mercury  in 
the  shorter  leg,  it  will  press  with  its  whole 
weight  on  the  included  air,  which  will  then 
be  found  to  occupy  4£  inches,  or  only  half 
of  its  former  space.  If,  in  like  manner,  the 
column  of  mercury  be  increased  to  twice  this 
length,  its  pressure  on  the  included  air  will 
be  tripled,  and  the  space  occupied  by  it  will 
be  reduced  to  one-third,  and  so  on  in  simple 
proportion.  It  consequently  happens  that 
at  a  pressure  of  seven  hundred  and  seventy 
Fig.  11.  atmospheres,  air  would  become  as  dense  as 


24.  What  is  the  relation  of  volume  to  density  in  the  air?    What  is  th« 
law  of  Mariotte ?    Explain  figure  11.     When  is  air  as  dense  as  water? 


THE    ATMOSPHERE. 


27 


vater.     The  terms  tension  and  density,  as  applied  to  gases, 
nave  the  same  meaning. 

25.  The  weight  of  the  atmosphere  is  of  course  shown  by 
<ne  air-pump.     The  receiver  is  fixed  by  the  first  stroke  of 
the  pump,  and  if  we  employ  on  the  plate  a  small  glass, 
)pen  at  both  ends,  (fig.  12,)  and  cover  the 

upper  end  with  the  hand,  we  shall  find  it 
fixed  with  a  powerful  pressure.     This  is 
vulgarly  called  suction,  but  is  plainly  due 
jnly  to  the  weight  of  air  resting  on  the  sur- 
face of  the  hand,  and  rendered  sensible 
6y  the  partial  withdrawal  of  the  air  be- 
low.    Hence,  all  vessels  of  glass  used  on  FiS- 12« 
the  air-pump  are  made  strong,  and  of  an  arched  form,  to 
resist  this  pressure.     Square  vessels  of  thin  glass  are  imme- 
diately crushed  on  submitting  them  to   the  at- 
mospheric pressure,  or  exploded  by  the  removal 
of  the  surrounding  air  while  they  are  sealed.  The 
weight  of  the  air  is  also  well  shown  by  the  burst- 
ing of  a  piece  of  bladder-skin  tied  tightly  over 
the  mouth  of  an  open  jar  on  the  plate  of  the 
air-pump.     As  the  pump  is  worked,  the  flat  sur- 
face of  the  bladder  becomes  more 
and  more  concave,  and  at  length 
bursts   inward  with   a  smart   ex- 
plosion. 

26.  Numerous  common  facts  and 
experiments    illustrate   the    same 
thing.  Were  the  atmospheric  pres- 
sure removed  from  under  our  feet, 
we  should  be  unable  to  move ;  and 
the  difficulty  we  experience  when 
walking  on  clay  is  due  to  a  partial 
vacuum  formed  by  the  close  con- 
tact of  the  foot  to  the  plastic  soil, 
excluding   the   air.      Boys   raise 
bricks  and  stones  by  a  "  sucker" 
of  moist  leather,  on  the  same  prin- 
ciple.     The  power   of  the   atmo- 
spheric pressure  to  raise  heavy  weights  is  well  shown  in  the 


Fig.  13. 


25.  What  Illustrations  of  the  weight  of  the  air  are  given  in  figs.  12  and 
13  ?     26.  How  is  the  weight  raised  in  fig.  14? 


28  MATTER 

annexed  apparatus,  (fig.  14.)  A  glass  jar,  having  an  open 
bottom,  is  covered  with  impervious  caoutchouc.  When  a 
vacuum  is  produced  in  the  jar,  the  yielding  cover  rises, 
carrying  with  it  a  weight  which  is  below.  This  is  sustained 
in  the  air,  as  by  an  elastic  spring.  The  amount  of  the  atmo- 
spheric pressure  has  been  experimentally  determined  as  equal 
to  fifteen  pounds  on  every  square  inch  of  surface.  This  fact 
is  demonstrated  by  the 

27.  Barometer. — This  instrument  (as  its  name  implies) 
enables  us  to  weigh  the  air.  It  was  discovered  by  Torricelli, 
an  Italian  philosopher,  in  the  year  1643.  When  a 
glass  tube,  (fig.  15,)  sealed  atone  end,  and  about  36 
inches  long,  is  filled  with  mercury,  the  open  end  closed 
by  the  finger,  and  inverted  in  a  vessel  containing  mer- 
cury, so  that  the  open  end  may  be  beneath  the  sur- 
face, so  soon  as  the  finger  is  withdrawn  the  mer- 
curial column  is  seen  to  fall  some  distance,  and, 
after  several  oscillations,  to  come  to  rest  at  a  cer- 
tain point,  where  it  is  apparently  stationary.  At 
the  level  of  the  sea,  this  point  is  found  to  be  about 
30  inches  above  the  surface  of  the  mercury  in  the 
basin.  The  empty  space  above  the  mercury  is  the 
most  perfect  vacuum  that  can  be  produced ;  and, 
in  honor  of  its  discoverer,  is  called  the  Torricellian 
vacuum. 

The  mercury  is  sustained  at  this  height  by  the 
pressure  of  the  atmosphere  on  the  surface  of  the 
fluid  in  the  basin,  and  the  height  of  the  column 
varies  with  the  atmospheric  pressure,  and  with  tue 
elevation  of  the  instrument  above  the  level  of  the 
ocean.  Had  water  been  the  fluid  employed,  it  would 
have  required  a  tube  more  than  34  feet  long  to 
accommodate  the  column.  If  the  experiment  be 
tried  above  the  ocean  level,  as  on  the  top  of  a  lofty 
mountain,  the  column  of  mercury  will  be  found  of 
a  less  elevation  in  proportion  to  the  height  of  the 
mountain.  It  was  the  distinguished  Pascal  who 
first,  in  1647,  suggested  this  experiment  on  the  top 
Fig.  15.  of  a  mountain  in  France,  as  conclusive  proof  that 


27.  What  is  the  barometer?  Describe  its  principle  ?  What  is  the  To- 
ricellian  vacuum?  Why  is  30  inches  the  height?  What  was  Pascal'* 
suggestion  ? 


THE   ATMOSPHERE.  29 

it  was  the  weight  of  the  air  which  sustained  the  mercury  in 
the  barometer. 

28.  The  principle  of  the  barometer  is  beautifully  shown  in 
fig.  16.     A  large  bell-glass,  with  a  wide  mouth  c,  has  two  sy- 
phon barometer  tubes  attached.    One  a  has  the  mercury  stand- 
ing at  the  proper  height  at  a,  while  its  cistern  enters  the  bell. 
The  other  tube  at  one  end  also  enters  the  bell,  but,  bending 
upon  itself,  it  holds  a  portion  of  mercury  in  the  outer  cis- 
tern b  on   its   other  extremity.     When    this  apparatus  is 
placed  on  the  air-pump  and  exhausted  of  air,  the 
mercury  a  falls  in  proportion  to  the  vacuum  pro- 
duced, while  that  in  b  mounts  in  like  proportion. 

In  &  we  see  the  effect  of  diminished  pressure,  as 
on  a  mountain  or  in  a  balloon ;  in  b  the  pressure 
of  the  external  air  causes  the  mercury  in  it  to 
mount,  forming  a  gauge  of  the  exhaustion. 

29.  If  the  tube  of  the  barometer  has  an  area 
of  one  inch,  and  the  height  of  the  column  is  30 
inches,  the  weight  of  the  mercury  sustained  in  it 
is  by  experiment  found  to  be  fifteen  pounds.  And 
this  is  the   pressure  which  the   atmosphere  ex- 
ercises on  every  square  inch  of  the  earth's  sur- 
face.    A   column   of  atmospheric   air   one   inch 
square,  and  reaching  to  the  uppermost  limits  of 
the  aerial  ocean,  will  also  weigh,  of  course,  just 
fifteen   pounds.     We  thus  come   to   regard   the 
mercury  in  the  barometer  as  the  equipoise  on  one 
arm   of  a  balance,  of  which  the  counterpart   is 
the   atmospheric   column.     As  the    latter  varies 

daily    from    meteoric   causes,    so   also   does   the    Fi    16 
height  of  the  mercurial  column  oscillate  in  just 
proportion.      Hence   the    barometer  is   properly   called   a 
"  weather-glass,"  and  by  its  movements  we  judge  of  the 
approach  of  storms.     These   changes    of  level  sometimes 
amount   at   the  same  place  to  2  or  2£   inches,  although 
usually  they  are  much  less. 

Various  forms  of  the  barometer  are  in  use  :    those  for 
measuring  the  elevation  of  mountains  are  so  constructed 


28.  How  is  the  principle  of  the  barometer  explained  in  fig.  16  ?  Why 
does  the  mercury  in  a  fall?  Why  does  that  in  b  rise?  29.  What  is 
the  pressure  of  air  on  a  square  inch  of  surface?  How  is  this  shown  by 
the  barometer  ?  How  is  the  barometer  a  weather-glass  ? 


30 


MATTER. 


as  to  be  easily  transported.  A  good 
form  of  the  mountain  barometer  is 
shown  in  fig.  17,  supported  on  a  tri- 
pod, which,  with  the  instrument,  can 
be  safely  packed  in  a  leather  case. 

30.  The  Aneroid  Barometer  is  de- 
signed to  supersede  the  mercurial  in- 
strument in  those  situations  where  the 
oscillating  motion  of  the  mercury  de- 
stroys the  value  of  its  indications,  as  in 
travelling,  in  aeronautical  excursions,  at 
sea,  and  on  many  other  occasions  when 
the  common  barometer  is  inconve- 
nient. It  depends  on  the  variation 
in  form  of  a  thin  vase  D  D  (fig.  18) 
of  copper,  which  being  partially  ex- 
hausted of  air  changes  its  dimensions 
with  every  variation  in  atmospheric 
pressure.  These  motions  are  multi- 
plied and  transferred  by  the  combina- 
tion of  levers  C,  K,  1,  2,  and  3,  &c., 
in  such  a  manner  that  the  index 
reads  the  barometric  conditions  of 
the  atmosphere  on  a  dial.  The  in* 
dex  is  set  by  adjusting  screws,  to 
correspond  with  a  standard  mer- 
curial instrument,  and  the  accuracy 
of  each  aneroid  is  tested  by  the  air- 
pump. 

31.  Weight  of  the  Atmosphere. — One  hundred  cubic  inches 
of  atmospheric  air  at  30  inches  of  the  barometer  and  60°  Fahr. 
weigh  30T832093  grains,  while  the  same  bulk  of  water  would 
weigh  about  25,250  grains.  Air  of  the  above  condition  is  as- 
sumed  as  the  standard  unity  for  the  density  of  all  other  aeri- 
form bodies.  A  man  of  ordinary  size  has  a  surface  of  about 
15  square  feet,  and  he  must  consequently  sustain  a  pressure 
on  his  body  of  over  1 5  tons.  This  prodigious  load  he  bears 
about  with  him  unconsciously,  because  the  mobility  of  the 
particles  of  air  causes  it  to  bear  with  equal  force  on  every 


Fig.  17. 


30.  What  is  the  aneroid  barometer?    31.  What  is  the  weight  of  air? 
What  weight  of  air  docs  a  man  sustain  ? 


WEIGHT   AND   SPECIFIC   GRAVITY.  31 

part  of  his  body,  beneath  his  feet  as  well  as  on  his  head, 
and  in  the  inner  cavities  as  well  as  on  the  outer  surface. 

32.  Limits  of  the  Atmosphere. — A  person  who  has  risen 
in  a  balloon,  or  on  a  mountain,  to  the  height  of  2*705  miles, 
or  14,282  feet,  has  passed  through  one-half  of  the  entire 
weight  of  the  air,  and  finds  his  barometer  to  indicate  this  by 
standing  at  15  inches. 

The  air  grows  more  and  more  rare  as  we  ascend,  and  tho 
barometer  falls  in  exact  proportion.  The  inconvenience 
which  travellers  have  experienced  in  ascending  high  moun- 
tains has,  it  is  said  on  good  authority,  been  very  much  ex- 
aggerated. The  heart  continues  its  action  under  a  diminished 
external  pressure,  and  no  serious  consequences,  it  is  believed, 
ever  follow,  as  the  bursting  of  bloodvessels  or  lesion  of  the 
lungs,  as  some  have  asserted.  On  the  summit  of  Chimbo- 
razo,  Baron  von  Humboldt  found  that  his  barometer  had 
sunk  to  13  inches  11  lines ;  and  the  same  philosopher  de- 
scended into  the  sea  in  a  diving-bell  until  the  mercurial  co- 
lumn rose  to  45  inches :  he  consequently  has  safely  expe- 
rienced a  change  of  31  inches  of  pressure  in  his  own  person. 

The  upper  limits  of  the  atmosphere  cannot  be  determined 
very  accurately ;  but,  from  the  refraction  of  light  as  observed 
in  the  rising  and  setting  of  stars,  astronomers  have  inferred 
that  it  is  probably  about  forty-five  miles  high. 

Weight  and  Specific  Gravity. 

33.  Weight  is  the  measure  of  the  force  of  gravity,  and 
is  directly  proportional  to  the  quantity  of  matter  in  a  given 
space.     Weight  is  determined  by  the  balance,  an  instru- 
ment to  which  the  chemist  appeals  at  every  step  of  his  in- 
vestigations.    Modern  instruments  enable  us  to  determine 
this  element  of  accurate  science,  to  the  greatest  nicety. 

The  specific  gravity  of  a  body  is  its  weight  as  compared 
with  an  equal  bulk  of  some  other  substance  assumed  as  the 
unit  of  comparison.  A  cubic  inch  of  gold  is  more  than  19 
times  as  heavy  as  a  cubic  inch  of  ice  or  of  water :  hence  the 
gold  is  said  to  have  a  specific  gravity  of  19,  compared  with 
water. 

Pure  water  has  been  adopted  as  the  standard  of  compari- 

32.  What  is  the  height  of  the  atmosphere?  33.  What  is  weight? 
What  is  specific  gravity  ?  What  is  the  standard  of  specific  gravity  ? 


MATTER. 


son  for  the  specific  gravity  of  all  solid  and  liquid  substances, 
taken  at  60°  Fahrenheit.  For  gases  and  vapours,  common 
air,  dry  and  at  the  temperature  of  60°  and  30  inches  of  ba- 
rometric pressure,  is  the  standard  assumed.  Regard  is  had 
to  the  conditions  of  temperature  and  pressure  because  the 
bulk  of  all  bodies  varies  sensibly  with  these  conditions. 

34.  The  specific  gravity  of  solids  is  determined  by  the 
theorem  of  the  renowned  Archimedes,  that  "  when  a  body 
is  immersed  in  water,  it  loses  a  portion  of  its  weight  exactly 
equal  to  the  weight  of  the  water  displaced."  He  thus  de- 
tected the  fraud  of  the  goldsmith  who  fur- 
nished to  King  Hiero  of  Syracuse,  as  a  crown 
of  pure  gold,  one  fashioned  of  base  metal — the 
specific  gravity  of  the  debased  alloy  was  too 
small  for  gold.  It  is  plain  that  a  solid  dis- 
places, when  immersed,  exactly  its  own  bulk 
of  water,  and  loses  weight  to  a  corresponding 
amount.  Hence,  if  we  weigh  a  body  first 
in  air  and  then  in  water,  the  loss  of  weight  ob- 
served, is  equal  to  the  volume  of  water,  cor- 
responding to  the  bulk  of  the  solid.  Fig.  19 
shows  a  group  of  crystals  of  quartz  suspended 
from  the  underside  of  the  scale-pan  by  a  fila- 
ment of  silk.  Its  weight  in  air  was  previously 
determined.  Its  diminished  weight  in  the 
water,  subtracted  from  the  weight  in  air,  gives 
Fig.  19.  a  sum  equal  to  the  bulk  of  water  displaced. 
From  these  elements  is  deduced  the  rule  to  find  the  specific 
gravity  of  a  solid.  "  Subtract  the  weight  in  water  from 

the  weight  in 
air,  divide  the 
weight  in  air 
by  this  dif- 
ference, and 
the  quotient 
will  be  the 
specific  gra- 
vity/' Fig. 

(  20  shows  the 

Fig.  20.  balance      ar- 


How  is  it  determined  ?  What  is  the  theorem  of  Archimedes  ?   34.  How 
is  this  illustrated  in  fig.  19  ?     Give  the  rule  for  specific  gravity 


WEIGHT   AND   SPECIFIC   GRAVITY. 


ranged  for  taking  the  specific  gravity  of  the  solid  a  sus- 
pended in  water  from  the  hook  b.  A  single  example  will 
serve  to  illustrate  this  rule.  We  find,  on  trial,  that  the 

Weight  of  a  substance  in  air,  is  .....................     357*95  grs. 

Weight  of  the  substance  in  louter  ..................     239-41  " 

Difference  ..........................................     118-44  " 

*~  3'01  sPeci 


Fig.  21. 


35.  The  specific  gravity   of  sub- 
stances lighter   than  water  may  be 
determined  by  attaching  them  to  a 
mass   of   lead   or   brass,    of  known 
weight  and   density.     Subtances   in 
small   fragments  or   in    powder  are 
placed  in   a   small   bottle,   fig.    21, 
holding,    for    example,    a    thousand 
grains  of  water.     Those   soluble   in 
water  are  weighed  in  a  fluid  in  which 
they   are  insoluble    and   whose  den- 
sity  is   separately  determined.      In 
these  cases  a  simple  calculation  re- 
fers the    results   to  the  known  den- 
sity of  pure  water. 

36.  The  specific  gravity  of  liquids  may 
be  ascertained  in  a  small   bottle   holding 
a  known  weight   of   pure  water.      These 
bottles  usually  have  a  small  perforation  in 
the  stopper,  as  seen  in  the  figure  22,  through 
which  the  excess  of  fluid  gushes  out,  and 
may  be  removed  by  careful  wiping.      The 
weight   of   the   bottle,  dry  and  empty,  is 
counterpoised   by  a  weight   kept  for  that 
purpose.  Fig.  22. 

37.  The  Hydrometer  is  an  instrument  of  great  use  in  de- 
termining the  specific  gravity  of  liquids  without  a  balance. 
It  is  simply  a  glass  tube,  fig.  23,  with  a  bulb  blown  on  one 
end  of  it,  containing  a  few  shot,  to  counterbalance  the  instru- 
ment ;  and  a  paper  scale  of  equal  parts  is  sealed  within  the 


Give  an  example.  35.  How  is  specific  gravity  determined  on  bodies 
lighter  than  water?  on  powders?  on  soluble  substances?  36.  On  fluida? 
37.  What  is  the  hydrometer?  Describe  its  use. 

a 


34 


MATTER. 


stem.  This  scale  indicates  the  points  to  which  the  stem  sinks 
when  immersed  in  fluids  of  different  den- 
sities. The  fluid,  for  convenience,  is 
placed  in  a  tube  or  narrow  jar,  (fig.  24): 
the  more  dense  the  liquid  is,  the  less 
quantity  will  the  hydrometer  displace, 
while  in  a  lighter  fluid  it  will  sink  deeper. 
The  zero  point  of  the  scale  is  always 
placed  where  the  instrument  will  rest  in 
pure  water,  after  which  the  graduation 
is  effected  on  a  variety  of  arbitrary  scales, 
all  of  which  can,  however,  be  referred  to 
the  true  specific  gravity  by  calculation, 
or  by  reference  to  a  table  such  as  may  bo 
found  at  the  close  of  this  volume.  Hy- 
dromcters  are  also  prepared  with  the  true 
lg'  *  1S'  '  specific  gravities  marked  upon  them,  read- 
ing even  to  the  third  decimal  place  accurately.  The  scales 
of  these  instruments  read  either  up  or  down,  according  as  the 
fluid  to  be  measured  is  either  heavier  or  lighter  than  water. 
In  case  of  alcohol,  the  graduation  of  the  hydrometer  is  made 
to  indicate  the  number  of  parts  of  pure  alcohol  in  a  hundred 
parts  of  a  liquid — absolute  alcohol  being  100,  and  water  0. 
The  hydrometers  of  Baume"  (French  scale)  are  much  used 
in  the  arts.  These  instruments  are  of  the  greatest  service 
to  the  manufacturer,  and,  when  carefully  made,  are  suffi- 
ciently accurate  for  most  purposes  of  the  laboratory.  They 
should  always  be  proved  by  comparison  with  the  balance 
and  thermometer  before  they  are  accepted  as  standards. 
For  many  purposes  they  are  made  of  brass  or  ivory,  as  well 
as  of  glass. 

Little  lalloons  or  lulls  of  glass,  are  frequently 
employed  to  find,  in  a  rough  way,  the  density  of 
fluids.  When  several  of  them  are  thrown  in  a 
fluid  of  known  density,  some  will  sink,  some  rise 
even  with  the  surface,  and  others  will  just  float. 
Those  which  just  float  are  taken,  and  being 
-  25<  marked  (as  in  fig.  25)  with  the  density  of  the 
liquid  which  they  represent,  are  then  used  to  determine  the 
specific  gravity  of  liquids  of  unknown  density.  They  are 
called  specific  gravity  bulbs,  arid  are  of  great  service  in  as- 

What  scales  are  used  in  Hydrometers?     What  use  is  made  of  little 
bulbs  of  glass' 


SPECIFIC   GRAVITY   OF   OASES. 


35 


certaining  the  density  of  gases  reduced  to  a  liquid  by  pres- 
sure in  glass  tubes,  when,  from  the  circumstances  of  the 
experiment,  all  the  usual  modes  of  ascertaining  specific  gra- 
vity are  inapplicable. 

38.  The  water  balloon,  or   "  Cartesian  devil,"  is  an  ele- 
gant illustration  of  the  law  of  specific  gravity.     In  this  toy 
the  balloon,  or  figure,  contains  a  portion  of  water 

just  sufficient  to  enable  it  to  float.  It  is  placed 
in  a  tall  jar  of  water,  over  the  top  of  which  is  tied 
a  cover  of  India-rubber.  Pressure  upon  this  cover 
forces  an  additional  quantity  of  water  into  the 
balloon  by  an  opening  (vt  fig.  26).  The  density 
of  the  mass  is  thus  increased,  and  it  sinks  until 
the  pressure  is  removed,  when,  the  air  in  the  bal- 
loon expanding,  forces  out  the  superfluous  water, 
and  the  glass  rises  again.  Such  is  the  mode  pro- 
vided by  nature  in  the  structure  of  the  nautilus 
and  ammonite,  by  which  means  those  curious  ani-  pjg.  26. 
mals  are  able,  at  will,  to  rise  or  sink  in  the  ocean. 

39.  Specific  Gravity  of  Gases. — It  remains  only,  under 
this  head,  to  speak  of  the  modes  used  for  determining  the 
specific  gravity  of  gases  and  vapors.      For  this  purpose  a 

globe,  (fig.  28,)  or  other  conveniently  formed  glass 
vessel,   holding  a  known    quantity    by   measure, 
(usually  100  cubic  inches,)  is  care-, 
fully   freed    from    air    and    mois- 
ture, by  the  air-pump  or  exhausting 
syringe.      It    is    then    filled    with 
the    gas    or  vapor   in  question,   at 
60°  Fahrenheit,  and  30  inches  of 
l_  a      the  barometer,  (33,)  and  weighed. 
The  weight  of  the  apparatus  filled 
with   common  air  being  previously 
known,  the  difference   enables  the 
experimenter  to  make  a  direct  com- 
parison.  Figure  27  shows  an  appa- 
ratus for  this  purpose;  the  globe  b 
jug.  -t{.   -g  proved  with   a  stopcock  e,  and  fitted  by  a 
screw  to  the  air-jar  a.     The  jar  is  graduated  so  that  the 
quantity  of  air  or  other  gas  entering  may  be  known  from 

38.  What  is  the  water  balloon.  What  animal  has  the  same  principle? 
How  is  air  weighed?  39.  Describe  figures  27  and  28.  How  do  we  find 
its  specific  gravity  of  gases  ? 


86  CRYSTALLIZATION. 

the  rise  of  the  water  in  a.  It  is  thus  found  that  100  cu- 
bic inches  of  pure  dry  air  weigh  30-829  grains,  while  the 
same  quantity  of  hydrogen  gas  weighs  only  2-14  grains, 
being  about  fourteen  times  lighter  than  air.  To  dry  the  air 
or  gas  it  must  be  made  to  pass  through  a  chlorid  of  calcium 
tube,  or  other  drying  apparatus;  before  entering  the  balloon. 


CRYSTALLIZATION. 
Nature  of  Crystallization  and  Forms  of  Crystals. 

40.  Nature  of  Crystallization. — The  forms  of  living  na- 
ture, both  animal  and  vegetable,  are  determined  by  the  laws 
of  vitality,  and  are  generally  bounded  by  curved  lines  and 
surfaces.     Inorganic  or  lifeless  matter  is  fashioned  by  a  dif- 
ferent law.     Geometrical  forms,  bounded  by  straight  lines 
and  plane  surfaces,  take  the  place  in  the  mineral  kingdom 
which  the  more  complex  results  of  the  vital  force  occupy 
in  the  animal  and  vegetable  world.     The  power  which  de- 
termines the  forms  of  inorganic  matter  is  called  crystalliza- 
tion.    A  crystal  is  any  inorganic  solid,  bounded  by  plane 
surfaces  symmetrically  arranged  and  possessing  a  homoge- 
neous structure.  * 

Crystallization  is,  then,  to  the  inorganic  world,  what  the 
power  of  vitality  is  to  the  organic ;  and  viewed  in  this,  its 
proper  light,  the  science  of  crystallography  rises  from  being 
only  a  branch  of  solid  geometry  to  occupy  an  exalted  philo- 
sophical position. 

The  cohesive  force  in  solids  is  only  an  exertion  of  crystal- 
line forces,  and  in  this  sense  no  difference  can  be  established 
between  solidification  and  crystallization.  The  forms  of 
matter  resulting  from  solidification  may  not  always  be  re- 
gular, but  the  power  which  binds  together  the  molecules  is 
that  of  crystallization. 

41.  Circumstances  influencing  Crystallization. — Solution 
is  one  of  the  most  important  conditions  necessary  to  crystal- 
lization.    Most  salts  and  other  bodies  are  more  soluble  in 
hot   than   in    cold  water.     A  saturated    hot   solution  will 
usually  deposit  crystals  on  cooling.      Common  alum  and 
Glauber's  salts  are  examples  of  this.     Solution  by  heat,  or 

How  mucfc  do  we  thus  find  the  air  to  weigh  ?  40.  What  is  crystalliza- 
tion said  to  be  ?  What  is  the  cohesive  force  ?  41.  Name  some  circum- 
stances which  influence  crystallization. 


POLARITY   OF   MOLECULES. 


37 


fusion,  also  allows  of  crystallization,  as  is  seen  in  the  crystal- 
line fracture  of  zinc  and  antimony.  Sulphur  crystallizes 
beautifully  on  cooling  from  fusion,  and  so  do  bismuth  and 
some  other  substances.  The  slags  of  iron-furnaces  and  sco- 
T'ISQ  of  volcanic  districts  present  numerous  examples  of  mine- 
rals finely  crystallized  by  fire.  Numerous  minerals  have 
been  formed  by  heating  together  the  constituents  of  which 
they  are  composed.  Blows  and  long-continued  vibration 
produce  a  change  of  molecular  arrangement  in  masses  of 
solid  iron  and  other  bodies,  resulting  often  in  the  formation 
of  broad  crystalline  plates.  Rail-road  axles  are  thus  fre- 
quently rendered  unsafe.  In  short,  any  change  which  can 
disturb  the  equilibrium  of  the  particles,  and  permits  any 
freedom  of  motion  among  them,  favours  the  reaction  of  the 
polar  or  axial  forces,  (42,)  and  promotes  crystallization. 

42.  Polarity  of  Molecules. — The  laws  of  crystallization 
show  that  the  molecules  have  polarity.  That  is,  these  mole- 
cules have  three  imaginary  axes  passing  through  them,  whose 
terminations,  or  poles,  are  the  centre  of  the  forces  by  which 
a  series  of  similar  particles  are  attracted  to  each  other  to 
form  a  regular  solid.  These  molecules  are  either  spheres 
(fig.  29)  or  ellipsoids,  (fig.  31,)  and  the  three  axes  (N  S) 


Fig.  29.  Fig.  30.  Fig.  31. 

are,  always,  either  the  fundamental  axes,  or  the  diameters  of 
these  particles.  In  the  sphere  (fig.  29)  these  axes  are  always 
of  equal  length,  and  at  right  angles  to  each  other,  and  the 
forms  which  can  result  from  the  aggregation  of  such  spheri- 
cal particles  can  be  only  symmetrical  solids,  such  as  the 
cube  and  its  allied  forms.  The  cube  drawn  about  the  sphere 
(fig.  29)  may  be  supposed  to  be  made  up  of  a  great  number 
of  little  spheres  (fig.  30)  whose  similar  poles  unite  N  and 
S.  In  the  ellipsoid  (fig.  31)  all  the  axes  may  vary  in  length, 

42.  What  do  the  laws  of  crystallization  show?  What  are  the  ayes  of 
molecules?  What  forms  have  the  molecules  of  bodies?  What  forms  C^D 
come  from  the  spherical  particles  ?  How  may  the  structure  of  the  cube 
be  shown  ?  How  are  the  axes  of  the  ellipsoid  ? 


38  CBYSTALLIZATION. 

giving  origin  to  a  vast  diversity  of  forms.  Under  the  in- 
fluence of  heat,  the  crystallogenic  attraction  loses  its  polarity 
and  force,  and  the  body  becomes  liquid  or  gaseous,  and  sub- 
ject to  repulsive  force.  The  return  to  a  solid  state  can  occur 
again  only  when  the  attractions  become  polar  or  axial. 

43.  Crystalline  Forms. — The  mineral  kingdom  presents  as 
with  the  most  splendid  examples  of  crystals.      In  the  labora- 
tory we  can  imitate  the  productions  of  nature,  and  in  many 
cases  produce  beautiful  forms  from  the  crystallization  of 
various  salts,  which  have  never  been  observed  in  nature. 
The  learner  who  is  ignorant  of  the  simple  laws  of  crystal- 
lography, sees  in  a  cabinet  of  crystals  an  unending  variety 
and  complexity  of  forms,  which  at  first  would  seem  to  baffle 
all  attempts  at  system  or  simplicity.    Numerous  as  the  natu- 
ral forms  of  crystals  are,  however,  they  may  be  all  reduced 
to  six  classes,  comprising  only  thirteen  or  fourteen  forms. 
From  these  all  other  crystalline  solids,  however  varied,  may 
be  formed  by  certain  simple  laws. 

44.  The  first  class  of  crystalline  forms  includes  the  cube, 
(fig.  32,)  the  octahedron,  (fig.  33,)  and  the  dodecahedron, 

(fig.     34.)        The 
faces  of  the  cube 
,    are  equal  squares. 
The     eight     solid 
angles  are  similar, 
and  also  the  twelve 
Fig.  32.  Fig.  33.  Fig.  34.       edges.     The  three 

axes  are  equal,  (aa,  bb,  cc,)  and  connect  the  centres  of  op- 
posite faces.  The  regular  octahedron  (fig.  33)  consists  of 
two  equal  four-sided  pyramids,  placed  base  to  base.  The  six 
solid  angles  are  equal,  and  so  also  the  edges,  which,  as  in 
the  cube,  are  twelve  in  number.  The  plane  angles  are  60°, 
and  the  interfacial  109°  28'  16".  The  axes  connect  the 
opposite  angles ;  they  are  equal  and  intersect  at  right  angles. 
This  class  is  also  called  the  monometric,  (inonos,  one;  and 
metron,  measure,)  the  axes  being  equal. 

45.  The  second  class  includes  the  square  prism  (fig.  35) 
and  square  octahedron  (fig.  36.)     In  the  square  prism  (fig. 
85)  the  eight  solid  angles  are  right  angles,  and  similar,  as  in 
the  cube.     The  eight  basal  edges  are  similar,  but  differ  from 


43.  How  are  the  complex  forms  of  crystals  arranged  and  simplified  ? 
44.  Describe  the  first  class  of  fundamental  forms. 


FORMS   OF   CRYSTALS. 


the  ibur  lateral.  The  two  basal 
faces  are  squares,  the  four  lateral 
are  parallelograms.  The  axes  con- 
nect the  centres  of  opposite  faces, 
and  intersect  at  right  angles. 
Square  prisms  vary  in  the  length 
of  the  vertical  axis,  (a,  a,)  which  is 
hence  called  the  varying  axis ;  the 


Fig.  35. 


Fig.  36. 


lateral  axes  (bb,  cc)  are  equal      This  class  is  also  called  the 
dimctriC)  (dis,  twofold,  and  metron,  measure.) 

46.  The  third  class  contains  the  rhombic  prism,  (fig.  37,) 
the  rectangular  prism,  (fig.  88,)  and  the  rhombic  octahedron, 
(fig.  39.)  The  rhom- 
bic prism  (fig.  37)  has 
two  sorts  of  edges,  two 
acute  and  two  obtuse. 
The  solid  angles  are, 
therefore,  of  two  kinds, 
four  obtuse  and  four 
acute.  The  axes  are 


Fig.  37. 


Fig.  38. 


Fig.  39. 


unequal  and  cross  at  right  angles.  The  lateral  connect  the 
centres  of  opposite  edges,  bb,  cc.  The  basal  faces  are  rhom- 
bic. The  rectangular  prism  (fig.  38)  has  all  its  solid  angles 
similar.  There  are  three  kinds  or  sets  of  edges,  four  lateral, 
four  longer  basal,  and  four  shorter  basal.  The  axes  connect 
the  centres  of  opposite  faces,  and  intersect  at  right  angles. 
The  three  are  unequal.  The  rhombic  octahedron  (fig.  39) 
has  three  unequal  axes,  connecting  opposite  solid  angles. 
All  the  sections  in  this  solid  are  rhombic.  This  class  is 
also  called  the  trimetric}  from  tris,  threefold,  and  metron , 
measure. 

47.  The  fourth  class  contains  the  oblique  rhombic  prism, 
(fig.  40,)  and  the  right  rhomboidal  prism,  (fig.  41.)  The 
oblique  rhombic  prism  is  represented 
in  the  figure  as  inclining  away  from 
the  observer,  the  prism  being  in  posi- 
tion when  standing  on  its  rhombic 
base.  The  upper  and  lower  solid 
angles  in  front  are  dissimilar,  one 
obtuse  and  the  other  acute.  The  four  lg' 


Fig.  41. 


45.  What  are  the  forms  of  the  second  class  ?  Describe  them.  46.  What 
forms  make  up  the  third  class  ?  Describe  them.  47.  What  forms  doea 
the  fourth  class  contain  ?  How  do  they  differ  ? 


40 


CRYSTALLIZATION1. 


lateral  solid  angles  are  similar.  Two  of  the  lateral  edges 
are  acute,  and  two  obtuse;  and  the  same  is  true  of  the  basal. 
The  lateral  axes  are  unequal;  they  connect  the  centres  of 
opposite  lateral  edges,  and  intersect  at  right  angles.  The 
vertical  axis  is  oblique  to  one  lateral  axis,  and  perpendicular 
to  the  other.  The  right  rhomboidal  prism  (fig.  41)  has  two 
obtuse  and  two  acute  lateral  edges,  and  four  longer  and  four 
shorter  basal  edges.  The  solid  angles  are  of  two  kinds, 
four  obtuse  and  four  acute.  The  axes  connect  the  centres 
of  opposite  faces;  one  is  oblique,  the  others  cross  at  right 
angles.  This  is  also  called  the  monoclinate,  (monos,  one, 
and  clino,  to  incline,)  having  one  inclined  axis. 

48.  The  fifth  class  includes  the  oblique  rhomboidal  prism. 

In  this  solid  only  those  parts  diagonally  opposite 
are  similar,  and  consequently  it  has  six  kinds  of 
edges.  The  axes  connect  the  centres  of  opposite 
faces.  They  are  unequal,  and  all  their  inter- 
sections are  oblique.  This  is  called  the  triclinate 
class,  from  tris,  three,  and  clino,  to  incline,  the 
lg*  '  three  axes  all  being  obliquely  inclined. 

49.  The  sixth  class  includes  the  hexagonal  prism  (fig.  43) 

and  the  rhombohedron, 
(figs.  44  and  45.)  The 
hexagonal  prism  has 
twelve  similar  angles, 
and  the  same  number  of 
similar  basal  edges.  The 
lateral  edges  are  six  in 
Fig.  43.  Fig.  44.  FiS- 45- number,  and  similar. 

The  lateral  axes  are  equal,  and  cross  at  60°,  connecting  the 
centres  of  opposite  lateral  faces  or  lateral  edges. 

The  rhombohedron  is  a  solid  whose  six  faces  are  all 
rhombs.  The  two  diagonally  opposite  solid  angles  (a  a) 
consist  of  three  equal  obtuse  or  equal  acute  plane  angles, 
and  the  diagonal  connecting  these  solid  angles  is  called  the 
vertical  axis,  (a  a.)  When  the  plane  angles  forming  the 
vertical  solid  angles  are  obtuse,  the  rhombohedron  is  called 
an  obtuse,  (fig.  44,)  and  if  acute,  it  is  called  an  acute  rhom- 
bohedron, (fig.  45.)  The  three  lateral  axes  are  equal,  and 

What  other  names  have  the  first,  second,  and  third  classes  ?  48.  What 
eolid  is  included  in  the  fifth  class?  49.  Name  the  two  solids  in  the  sixth 
class  of  fundamental  forms.  How  are  the  hexagonal  prisin  and  rhoinbo- 
liedron  related?  How  are  rhornbohedrons  distinguished? 


MEASUREMENT   OP   CRYSTALS. 


41 


intersect  at  angles  of  60° :  they  connect  the  centres  of  op- 
posite lateral  edges.  This  will  be  seen  on  placing  a  rhom- 
bohedron  in  position  and  looking  down  upon  it  from  above. 
The  six  lateral  edges  will  be  found  to  be  arranged  around 
the  vertical  axis,  like  the  sides  of  an  hexagonal  prism. 

50.  The  mutual  relations  of  the  forms  of  crystals  are  well 
shown  in  the  foregoing  arrangement.     Thus,  in  each  of  the 
six  classes,  the  first  named  solid  alone  is,  properly  considered, 
a  fundamental  form,  the  others  in  each  class  being  frequently 
found  as  secondaries  to  these.     The  six  fundamental  forms 
are  the  cube,  square  prism,  right  rectangular  prism,  oblique 
rhombic  prism  or  right  rhomboidal  prism,  oblique  rhomboi- 
dal  prism,,  and  the  hexagonal  prism  or  rhombohedron. 

51.  The  structure  of  crystals  is  often  seen  by  lines  on 
their  surfaces,  or  by  the  ease  with  which  the  crystal  splits 
in  certain  directions.     Common   mica  cleaves  in  leaves; 
galena  breaks  only  in  cubes,  fluor-spar  in  octahedra,  calc-spar 
only  in  rhombohedrons.     This  property  is  called  cleavage. 
It  does  not  exist  in  all  crystals,  and  is  not  of  equal  facility 
in  all  directions.     Thus,  in  mica,  cleavage  is  easy  in  one 
direction  only;  while  in  fluor-spar  and  calcite  it  is  equally 
easy  in  three  directions  respectively. 

Measurement  of  Crystals. 

52.  Common  Goniometer.* — The  angles  of  crystals  are 
measured  by  means  of  instruments  called  goniometers.    .The 
common    goniome- 
ter, which  is  here 

figured,  consists  of 
a  light  semicircle 
of  brass,  (fig.  47,) 
accurately  graduat- 
ed into  degrees,  and 
having  a  pair  of 
steel  arms  (fig.  46) 
moving  on  a  central 
pivot,  and  so  ar- 
ranged as  to  slip  in 

50.  What  is  said  of  the  relations  of  fundamental  forms  ?  What  six  fun- 
damental forms  are  named  ?  51.  What  is  cleavage  in  minerals  ?  On  what 
does  it  depend  ?  Give  examples.  Is  it  equal  in  all  minerals? 

*  From  the  Greek,  gonia,  an  angle,  and  metron,  measure. 


Fig.  46. 


Fig.  47. 


42 


CRYSTALLIZATION. 


a  groove  over  each  other.  The  points  a  a  can  thus  be  made 
to  embrace  the  faces  of  a  crystal  whose  angle  we  wish  to 
measure.  The  graduated  semicircle  is  applied  with  its  centre 
at  the  point  of  intersection,  when  the  angle  is  read  on  the 
arc.  Where  the  greatest  nicety  is  required,  a  much  more 
delicate  instrument  is  used. 

5d.  Wollaston's  Reflective  Goniometer. — The  principle  of 
this  instrument  may  be  understood  by  reference  to  fig.  48, 
which  represents  a  crystal  (o) 
whose  angle  (a  b  c)  is  required. 
The  eye  at  P,  looking  at  the  face 
(6  c)  of  the  crystal,  observes  a 
reflected  image  of  M  in  the  direc- 
tion of  P  N.  The  crystal  may 
now  be  so  turned  that  the  same 
image  is  seen  reflected  in  the  next 
face,  (b  a,)  and  in  the  same  direc- 
tion, (P  N.)  To  effect  this,  the  crystal  must  be  turned 
until  a  b  has  the  present  position  of  b  c.  The  angle  d  b  c 
measures,  therefore,  the  number  of  degrees  through  which 
the  crystal  must  be  turned.  But  d  b  c  subtracted  from 
180°  equals  the  required  angle  of  the  crystal  a  b  c;  con- 
sequently, the  crystal  passes  through  a  number  of  degrees, 
which,  subtracted  from  180°,  gives  the  required  angle. 

When  the  crystal  is  attach- 
ed to  a  graduated  circle,  we 
have  the  goniometer  of  Wol- 
laston,  which  is  represented 
in  fig.  49.  The  crystal  to 
be  measured  is  attached  aty', 
and  may  be  adjusted  by  the 
milled  head  c  and  arm  d, 
moving  independent  of  the 
great  circle  a.  When  adjust- 
ed in  the  manner  described 
above,  the  wheel  is  revolved 
until  the  image  of  M  is  seen 
Fig.  49.  in  the  second  face.  This 

movement  is  practically  a  subtraction  of  the  angle  a  b  c 


52.  What  is  a  goniometer?  Explain  the  common  one  and  its  use.  53. 
Explain  the  principles  of  Wollaston's  goniometer  from  figure  4.8.  HOT* 
is  this  principle  used  in  Wollaston's  instrument? 


SOURCES   AND   NATURE   OP   LIGHT.  43 

from  180°,  and  the  result  is  read  directly  by  the  vernier  e. 
— The  subject  of  crystallography  cannot  be  further  illustrated 
here;  but  the  learner  who  desires  to  pursue  it,  is  referred  to 
the  highly  philosophical  treatise  on  mineralogy  by  Professor 
J.  D.  Dana. 

II.  LIGHT. 

54.  The  physical  phenomena  of  light  properly  belong  to 
the  science  of  Optics,  a  branch  of  natural  philosophy  not 
necessarily  connected  with  chemistry.  A  knowledge  of  some 
of  the  laws  of  light  is;  however,  required  of  the  chemical 
student. 

55.  Sources  and  Nature  of  Light. — The  sun  is  the  great 
source  of  light,  although  we  know  many  minor  and  artificial 
sources.    Of  the  real  nature  of  light  we  know  nothing.     Sir 
Isaac  Newton  argued  that  it  was  a  material  emanation  from 
the  sun  and  other  luminous  bodies,  consisting  of  particles  so 
attenuated  as  to  be  wholly  imponderable  to  our  means  of 
estimating  weight,  and  having  the  greatest  imaginable  repul- 
sion to  each  other.  These  particles,  by  his  theory,  are  supposed 
to  be  sent  forth  in  straight  lines,  in  all  directions,  from  every 
luminous  body,  and,  falling  on  the  delicate  nerves  of  the 
eye,  to  produce  the  sense  of  vision.     This  is  called  the  New- 
tonian or  corpuscular  theory  of  light.     It  is  not  generally 
adopted  by  physicists,  but  the  language  of  optical  science  is 
formed  mainly  in  accordance  with  it.     The  other  view  or 
theory  of  light,  which  is  now  almost  universally  accepted, 
is  called  the  wave  or  undulatory  theory.     It  is  known  that 
sound  is  conveyed  through  the  air  by  a  series  of  vibrations 
or  waves,  pulsating   regularly  in   all    directions,  from  the 
original  source  of  the  sound.     In  the  same  manner  it  is 
believed  that  light  is  conveyed  to  the  eye  by  a  series  of  un- 
ending and  inconceivably  rapid  pulsations  or  undulations,  im- 
parted from  the  source  of  light  to  a  very  rare  or  attenuated 
medium,  which  is  supposed  to  fill  all  space.     This  medium 
is  called  the  luminiferous  ether. 

Astronomy  furnishes  evidence  of  the  presence  in  space 
of  a  medium  resisting  the  motion  of  the  heavenly  bodies 


54.  What  is  optics  ?  55.  Name  sources  of  light.  What  is  the  New- 
tonian hypothesis  ?  What  is  the  other  theory  ?  What  is  the  medium  of 
light?  What  evidence  does  astronomy  give  of  an  ether? 


44 


LIGHT. 


Encke's  comet  is  found  to  lose  about  two  days  in  each  sue 
cessive  period  of  1200  days.  Biela's  comet,  with  twice  that 
length  of  period,  loses  about  one  day.  That  is,  the  succes- 
sive returns  of  these  bodies  is  found  to  be  accelerated  by  this 
amount.  No  other  cause  for  this  irregularity  has  beeu 
found  but  the  agency  of  the  supposed  ether. 

56.  Undulations. — The  propagation  of  force  by  undula- 
tions, pulsations,  or  waves,  is  a  general  fact  in  physics.     A 
vibrating  cord  communicates  its  waves  of  motion  to  the  sur- 
rounding air,  and  a  musical  tone  results. 

If  a  long  cord  A  B,  fig.  50, 

— L  c       f    'y-<&W  be  jerked  by  the  hand,  the 

\^J  ***(£*  motion  is  propagated  from 
the  hand  A,  in  the  curve 
AC,  and  so  on  successively 
to  B,  when  the  motion  is 
again  reflected  in  the  oppo- 
site phase  to  the  hand,  as  in 
fig.  51,  where  the  continued 
line  shows  the  primary  vi- 
brations, and  the  dotted  one  that  which  is  reflected. 

A  pebble  dropped  on  the  surface  of  a 
quiet  pool,  produces  a  series  of  circular  waves 
receding  to  the  shore,  (fig.  52.)  The  waves 
produced  do  not  transport  any  light  bodies 
a  accidentally  floating  on  the  surface  of  the 
water.  These  only  rise  and  fall  as  each 
wave  passes. 

57.  The  measure  of  the  waves  on  the  surface  of  water  ia 
from  crest  to  crest,  or  from  hollow  to  hollow,  and'  in  every 

complete  wave  or  entire  vibration  (fig.  53) 
the  following  parts  are  recognised:  aebdc 
—j  -is  the  whole  length  of  the  wave ;  a  ebi    the 
phase  of  elevation,  and  bde  the  phase  of  de- 
pression.     The  height  of  the  wave  is  ef,  and 
1S'     '        its  depth  g  d.    The  points  in  which  the  phases 
of  elevation  and  of  depression  intersect,  as  in 
fig.  51,  are  called  nodal  points,  and  are  always  at  rest :  so 


Fig.  50. 


Fig.  51. 


Fig.  52. 


.  56.  How  is  force  propagated  ?  Illustrate  by  figs.  50  and  51.  Describe 
the  progress  of  waves  from  fig.  52.  57.  Name  the  parts  of  a  wave  in  fig. 
64.  Distinguish  the  phases  of  elevation  and  of  depression.  What  are 
U'.-dul  points? 


UNDULATIONS   01    LIGHT.  45 

that  light  bodies  resting  on  them  would  remain  undisturbed, 
which  placed  elsewhere  would  be  immediately'  thrown  off. 
If  two  waves  of  equal  altitude  and  arriving  from  opposite 
directions  unite,  so  that  the  elevations  and  depressions  of 
the  two  correspond,  then  the  resulting  wave  is  doubled. 
But  if  the  two  meet  at  half  the  distance  of  their  respective 
elevations  and  depressions,  'so  that  the  crest  of  one  corre- 
spond to  the  hollow  of  the  other,  then  both  are  obliterated, 
and  the  surface  becomes  quiet ;  or  if  one  wave  was  larger 
than  the  other,  a  third  wave,  corresponding  to  the  difference 
only  of  the  other  two,  results. 

58.  This  is  equally  true  whether  we  speak  of  waves  of 
sound,  of  heat,  of  light,  or  in  fluids.     That  two  waves  of 
sound  may  meet  so  as  to  produce  silence,  may  easily  bo 
shown  by  vibrating  a  tuning-fork  over  an  open 

glass  A,  and  holding  another  similar  glass  B  lip 
to  lip  with  the  first,  and  at  right  angles  with  it, 
as  shown  in  fig.  54.     The  vibrations  may  be 
increased  by  sticking  a  piece  of  circular  card- 
board on  one  leg  of  the  fork,  and  by  pouring 
water  into  the  first  glass  until  the  tone  is  ad-       Fig.  54. 
justed  to  a  maximum.     Or  a  second  fork  may 
be  used  in  place  of  B,  differing  half  a  tone  from  the  other 
fork,  (fig.  55.)     In  this  case  a  series  of  swells  and  cadences 
will  be  heard  in  place  of  entire  silence.     In  these 
cases,  the  waves  of  sound  interfere,  as  before,  in 
the  case  of  the  water.     In  like  manner,  two  cur- 
rents of  thermo-electricity  may  meet   in  such  a 
manner  as  to  freeze  a  drop  of  water  in  one  end  of 
the  arrangement,  the   current  being  excited  by 
heating  the  opposite  end  of  the  system. 

59.  So  two  rays  of  light,  AB,  CD,  fig.  56,    Fig  55> 
meeting  at  the  proper  interval,  (a,)  will  produce  a 

beam  of  double  intensity ;  but  if 
they  meet  at  the  half  interval  of 
vibration,  darkness  results.  This  j,io.  56 

is  interference  of  light.     In  mo- 
ther of  pearl  and  many  other  natural  bodies,  a  beautiful 
play  of  colors  is  seen.     The  microscope  reveals  on  such  sur- 


When  are  waves  made  double,  and  when  set  at  rest?  58.  Illustrate  the 
interference  of  waves  of  sound  in  figs.  54  and  55.  What  of  thermo- 
electricity ?  59.  Describe  the  interference  of  light  from  fig.  56. 


46  LIGHT. 

faces  delicate  grooves  and  ridges,  and  these  are  at  such  dis- 
tances as  to  produce  interference  in  the  light-waves,  result- 
ing in  partial  obscuration  and  partial  decomposition.  The 
same  effect  is  artificially  produced  in  medal-ruling.  This 
irised  effect  can  be  transferred  by  pressure  or  copied  by  the 
electrotype,  or  even  on  wax. 

60.  The  transverse  vibrations  of  a  ray  of  light  distinguish 
this  from  all  other  modes  of  undulation  or  vibration.     Dr. 

Bird  illustrates  this  by  fig.  57,  which  represents 
a  spherical  particle  of  ether  alternately  extended 
and  depressed  at  its  poles  and  equator,  oscilla- 
ting,   or  trembling,    rather   than   undulating. 
Thus,  each  particle  in  turn  communicates  the 
Fig.  57.     impulse  which  it  receives,  and  yet  the  centre 
of  each  may  remain  unmoved  from  its  place ; 
as  motion  in  a  series  of  ivory  balls  causes  only  the  termi- 
nal one  to  swing,  the  intermediate  ones  remaining  unmoved. 
In  light-waves,  the  vibration  or  pendulation  of  each  particle 
is  perpendicular  to  the  path  of  the  ray ;  and  yet  the  alternate 
effect  of  the  movements  of  contiguous  particles  will  produce 
a  progressive  vibration.     Thus,  in  fig. 
WaQ(Q\O)  '  58>  A  B  C  D  may  represent  particles  of 
A"    B     c     ii       ether  in  the  path  of  a  ray  of  light,  the 
Fig.  58.  phases   of  elevation   in  A  and    C   and 

those  of  depression  in  B  and  D  being 
coincident.  The  fact  of  the  vibrations  of  light-ether  being 
transverse  to  the  path  of  the  ray  was  first  observed  by  Fres- 
nel.  These  vibrations  are  conceived  to  occur  in  any  or  every 
transverse  plane.  Leaving  these  interesting  generalizations, 
we  must  briefly  recapitulate  the  well-established 

61.  Properties  of  Light. — 1st.  Light  is  sent  forth  in  rays 
in  all  directions  from  all  luminous  bodies.     2d.  Bodies  not 
themselves  luminous  become  visible  by  the  light  falling  on 
them  from  other  luminous  bodies.     3d.  The  light  which  pro- 
ceeds from  all  bodies  has  the  color  of  the  body  from  which 
it  comes,  although  the  sun  sends  forth  only  white  light.    4th. 
Light  consists  of  separate  parts  independent  of  each  other. 
5th.  Rays  of  light  proceed  in  straight  lines.     6th.  Light 
moves  with  a  wonderful  velocity,  which  has  been  computed 


What  instances  are  named  from  nature  ?  60.  What  are  transverse  vi- 
brations in  light?  How  is  the  undulation  thus  produced?  What  i?  said 
of  progressive  motion  ?  61.  Enumerate  six  properties  of  light. 


REFLECTION.  47 

by  astronomical  observations  to  be  at  least  one  hundred  and 
ninety-five  thousands  of  miles  in  a  second  of  time.  This 
velocity  is  so  wonderful  as  to  surpass  our  comprehension, 
Herschel  says  of  it,  that  a  wink  of  the  eye,  or  a  single  motion 
of  the  leg  of  a  swift  runner,  or  flap  of  the  wing  of  the  swiftest 
bird,  occupies  more  time  than  the  passage  of  a  ray  of  light 
around  the  globe.  A  cannon-ball  at  its  utmost  speed  would 
require  at  least  seventeen  years  to  reach  the  sun,  while  light 
comes  over  the  same  distance  in  about  eight  minutes. 

62.  When  a  ray  of  light  falls  on  the  surface  of  any  body, 
several  things  may  happen.     1st.  It  may  be  absorbed  and 
disappear  altogether,  as  is  the  case  when  it  falls  on  a  black 
and  dull  surface.    2d.  It  may  be  nearly  all  reflected,  as  from 
some  polished  surfaces.    3d.  It  may  pass  through  or  be  trans- 
mitted ;  and,  4th.  It  may  be  partly  absorbed,  partly  reflected, 
and  partly  transmitted.     All  bodies  are  either  luminous, 
transparent,  or  opake.     Bodies  are  said  to  be  opake  when 
they  intercept  all  light,  and  transparent  when  they  permit 
it  to  pass  through  them.     But  no  body  is  either  perfectly 
opake  or  entirely  transparent,  and  we  see  these  properties  in 
every  possible  degree  of  difference.   Metals,  which  are  among 
the  most  opake  bodies,  become  partly  transparent  when  rnado 
very  thin,  as  may  be  seen  in  gold-leaf  on  glass,  which  trans- 
mits a  greenish-purple  light,  and  in  quicksilver,  which  gives 
by  transmitted  light  a  blue  color  slightly  tinged  with  purple. 
On  the  other  hand,  glass  and  all  other  transparent  bodies 
arrest  the  progress  of  more  or  less  light. 

63.  Reflection. — Light  is  reflected  according  to   a   very 
simple  law.     In  fig.  59,  if  the  ray  of  light  fall  from  P'  to 
P,  it  is  thrown  directly  back  to  „, 

P';  for  this  reason,  a  person 
looking  into  a  common  mirror 
sees  himself  correctly,  but  his 
image  appears  to  be  as  far  behind 
the  mirror  as  he  is  in  front  of  it. 
The  line  P  P'  is  called  the  normal. 


If  the  ray  fall  from  R  to  P,  it  will 
be  reflected  to  R',  and  if  from  r, 
then  it  will  go  in  the  line  /,  and  so  for  any  other  point, 


Illustrate  its  velocity.  62.  What  happens  to  incident  light  ?  How  are 
bodies  divided  in  respect  to  light?  Give  illustrations  of  imperfect 
opacity.  63.  What  is  the  law  of  reflection  ?  What  is  the  normal  ? 


48 


LIGHT. 


[f  we  measure  the  angles  RPP'  and  P'PR',  we  shall  find 
them  equal  to  each  other,  and  so  also  the  angles  r  P  P'  and 
P'  P  /.  These  angles  are  called  respectively  the  angles  of 
incidence  and  reflection.  We  therefore  state  that  the  angle 
of  incidence  is  equal  to  the  angle  of  reflection,  which  is  the 
law  of  simple  reflection.  This  law  is  as  true  of  curved  sur- 
faces as  it  is  of  planes ;  for  a  curved  surface  (as  a  concave 
metallic  mirror)  is  considered  as  made  up  of  an  infinite 
number  of  small  planes. 

64.  Simple  Refraction. — If  a  ray  of  light  falls  perpendi- 
cularly on  any  transparent  or  uncrystallized  surface,  as  glass 
or  water,  it  is  partiy  reflected,  partly  scattered  in  all  direc- 
tions,   (which    part   renders   the 
object  visible,)  and  partly  trans- 
mitted in  the  same  direction  from 
-  ^  ___^i  which  it  comes.     If,  however,  the 
'^V         llf  light  come   in  any  other  than  a 
^=~1T~^  ^»  perpendicular  or  vertical  direction, 

as  from  R  to  A,  on  the  surface  of 
a  thick  slip  of  glass,  as  in  fig.  60, 
it  will  not  pass  the  glass  in  the 
line  RAB,  but  will  be  bent  or 
refracted  at  A,  to  C.  As  it  leaves 
the  glass  at  C,  it  again  travels  in 


Fig.  60. 


a  direction  parallel  to  R  A,  its  first  course.  Refraction,  then, 
is  the  change  of  direction  which  a  ray  of  light  suffers  on 
passing  from  a  rarer  to  a  denser  medium,  and  the  reverse. 
In  passing  from  a  rarer  to  a  denser  medium,  (as  from  air  to 
glass  or  water,)  the  ray  is  bent  or  refracted  toward  a  line 
perpendicular  to  that  point  of  the  surface  on  which  the  light 
falls;  and  from  a  denser  to  a  rarer  medium  the  law  is 
reversed. 

A  common  experiment,  in  illustration  of  this  law,  is  to 
place  a  coin  in  the  bottom  of  a  bowl,  so  situated  that  the 
observer  cannot  see  the  coin  until  water  is  poured  into  the 
vessel  ]  the  coin  then  becomes  visible,  because  the  ray  of 
light  passing  out  of  the  water  from  the  coin  is  bent  toward 


What  is  the  angle  of  incidence  ?  What  of  reflection  ?  What  is  true 
of  curved  surfaces?  64.  What  is  refraction?  Demonstrate  the  law  by 
fig.  60.  Which  way  is  the  ray  bent  ?  Give  a  familiar  illustration  of 
refraction. 


THE    PRISM.  49 

the  eye.     In  the  same  manner,  a  straight  stick  thrust  into 
water  appears  bent  at  an  angle  where  it  enters  the  water. 

65.  Index  of  Refraction. — The  obliquity  of  the  ray  to,  the 
refracting  medium  determines  the  amount  of  refraction.    The 
more  obliquely  the  ray  falls  on  the  surface,  the  greater  the 
amount  of  refraction.     A  little  modification  of  the  last  figure 
will  make  this   clear.     Let  R  A 

(fig.  61)  be  a  beam  of  light  falling 

on  a  refracting  medium  :  it  is  bent 

as  before  to  E/.    If  we  draw  a  circle 

about  A  as  a  centre,  and  let  fall 

the  line  a  a,  from   the  point  a, 

where  the  circle  cuts  the  ray  R, 

and  at  right  angles  to  the  normal 

A'  A,  the  line  a  a  is  called  the  sine 

of  the  angle  of  incidence ;   while 

the  line  a!  a'  is  called  the  sine  of  Fig.  61. 

the  anyle  of  refraction. 

If  a  more  oblique  ray  r  cuts  the  circle  at  b,  the  line  b  b 
will  be  longer  than  the  line  a  a,  inasmuch  as  the  angle  b  A 
a  is  greater  than  the  angle  a  A  a. 

The  line  measuring  the  obliquity  before  refraction,  when 
the  ray  passes  into  a  denser  medium,  is  always  greater  than 
that  which  measures  it  after.  The  ratio  of  these  lines  ex- 
presses the  refractive  power  of  the  medium.  This  is  called 
the  index  of  refraction. 

In  rain  water  the  ratio  of  these  lines  is  as  529  : 396  or 
1-31 ;  in  crown  glass  it  is  as  31 :  20  or  1-55;  in  flint  glass 
1-616,  and  in  the  diamond  243. 

66.  Substances  of  an  inflammable  nature,  or  rich  in  carbon, 
and  those  which  are  dense,  have,  as  a  general  thing,  a  higher 
refracting  power  than  others.     Sir  Isaac  Newton  observed 
that   the   diamond   and  water   had   both   high   refracting 
powers,  and  he  sagaciously  foretold  the  fact,  which  chemis- 
try has  since  proved,  that  both  these  substances  had  a  com- 
bustible base,  or  were  of  an  inflammable  nature. 

67.  Prism. — In  the  cases  of  simple  refraction  just  ex- 
plained, the  ray,  after  leaving  the  refracting  medium,  goes 
on  in  a  course  parallel  to  its  original  direction,  because  the 


65.  What  is  the  index  of  refraction  ?  Demonstrate  this  from  fig.  61. 
66.  What  substances  have  highest  refraction  ?  What  was  Newton'^  sug- 
gestion about  the  diamond  ? 


50 


LIGHT. 


Fig.  62. 


,R'  two  surfaces  of  the  medium  are  pa- 
rallel. If,  however,  the  surfaces  of  the 
refracting  medium  are  not  parallel, 
the  ray,  on  leaving  the  second  sur- 
face, will  be  permanently  diverted 
from  its  original  path.  ,  The  com- 
mon triangular  glass  prism  (fig.  62)  illustrates  this. 
As  already  explained,  the  ray  R  is  bent  toward  the 
normal  in  media  more  dense  than  air.     But  in  tho 
prism  the    emergent  ray  R  is,  by  the  same  law, 
still   farther  refracted   in   the  direction   R'.     By 
altering  the  form  of  the  surfaces,  we  may  thus 
send  the  ray  in  almost  any  direction,  as  in  the 
common   multiplying-glass,  which  gives  as  many 
images  as  it  has  surfaces  of  reflection.     In   this 
way  it  is  that  concave  metallic  mirrors  concentrate, 
and  convex  ones  disperse  a  beam  of  light.    Fig.  63 
shows  the  prism  conveniently  mounted  for  use. 
__  Analysis  of  Light.  —  By  means  of  the  prism, 

p-     63    Sir  Isaac  Newton  demonstrated  the  compound  na- 
ture of  white  light,  such  as  reaches  us  in  the  ordi- 

nary sunbeam.  In 
fig.  64  a  pencil  of 
rays  from  R,  fall- 
ing from  a  small 
circular  aperture 
in  the  shutter  of  a 
darkened  room  on 
a  common  trian- 
gular prism,  is  refracted  twice,  and  bent  upward  toward  the 
white  screen  R',  placed  at  some  distance  from  the  prism, 
where  it  forms  an  oblong  colored  image,  composed  of  seven 
colors.  This  image  is  called  the  prismatic  or  solar  spectrum. 
The  spectrum  has  the  same  width  as  the  aperture  admit- 
ting the  beam  of  light,  but  its  length  is  greatly  increased  be- 
yond its  diameter,  the  ends  retaining  the  rounded  form  of 
the  opening.  This  image  or  spectrum  presents  the  most 
beautiful  series  of  colors,  exquisitely  blended,  and  each  pos- 
sessing a  degree  of  intensity,  splendor,  and  purity  far  ex- 
ceedingly the  colors  of  the  most  brilliant  natural  bodies. 
These  colors  are  not  separated  by  distinct  lines,  but  seem  to 


64- 


67.  How  is  light  refracted  by  surfaces  not  parallel.    What  is  tho  prism  1 


PRISMATIC    COLORS. 


51 


SOLAR  SPECTRUM. 


melt  into  one  another,  so  that  it  is  impossible  to  say  where 
one  ends  and  the  next  begins. 

The  light  from  flames  of  all  kinds,  the  oxy-hydrogen 
blowpipe,  and  the  electric  spark,  or  galvanic  light,  is  also 
compound  in  its  nature,  like  that  of  the  sun  and  other  ce- 
lestial bodies. 

69.  Prismatic  Colors. — The  colors  of  the  solar  spectrum 
are  in  the  following  order,  reading  upward  :  red,  orange,  yel- 
low, green,  blue,  indigo,  violet.  These  colors  are  of  very 
different  refrangibility,  and  for  this  reason  are  presented  in 
a  broad  and  blended  surface,  the  red  being  the  least  refracted, 
and  the  violet  the  most.  The  seven  colors  of  Newton,  it 
is  believed,  are  really  composed  of  the  three  primitive  ones, 
red,  yellow,  and  blue.  This  idea  is  well  expressed  in  the 
following  diagram, 
(fig.  65.)  The  three 
primitive  colors 
each  attain  their 
greatest  intensity 
in  the  spectrum  at 
the  points  marked 
at  the  summit  of 
the  curves;  while 
the  four  other  co- 
lors, violet,  indigo,  green,  and  orange,  are  the  result  of  a 
mixture,  in  the  spectrum,  of  the  first  three.  A  portion  of 
proper  white  light  is  also  found  in  all  parts  of  the  spectrum, 
which  cannot  be  separated  by  refraction.  We  may  hence 
infer  that  there  is  a  portion  of  each  color  in  every  part  of 
the  spectrum,  but  that  each  is  most  intense  at  the  points 
where  it  appears  strongest.  The  light  is  most  intense  in  the 
yellow  portion,  and  fades  toward  each  end  of  the  spectrum. 

Sir  John  Herschel  has  detected  rays  of  greater  refrangibi- 
lity than  the  violet  of  the  spectrum  and  are  beyond  it,  which 
have  a  lavender  color.  They  have  this  color  after  concen- 
tration, and  are  therefore  not  merely,  as  might  be  supposed, 
dilute  violet  rays. 

If  the  spectrum  is  formed  by  a  beam  of  light  passing 
through  a  slit  not  over  -Mh  of  an  inch  in  width,  the  image 


65' 


68.  Describe  the  analysis  of  light.  What  is  the  image  called  ?  What 
is  the  form  of  the  spectrum?  How  are  the  colors  arranged?  Describe 
the  blending  of  the  colors  from  fig.  65.  What  is  lavender  light? 


52  LIOIIT. 

will  be  crossed  by  a  great  number  of  dark  lines,  which  al- 
ways appear  in  the  same  relative  position.  They  are  called 
the  fixed  lines  of  the  spectrum,  and  are  much  referred  to 
as  boundary  lines  in  optical  descriptions. 

70.  Each  of  the  prismatic  colors  has  some  other,  which 

blended  with  it  produces  white  light,  and  hence 
is  called  its  complementary  color.  Let  indigo  be 
regarded  as  a  deeper  blue,  and  each  of  the  three 
primary  colors  has  its  secondary  colors.  Fig. 
65  shows  the  three  primary  tints  blending  to 
Fig.65(4i«.)  form  white  light  at  the  centre:  at  the  other 
parts  the  complementary  colors  are  opposite  to  each  other, 
c.  g.  red  and  green,  blue  and  yellow. 

71.  Double   refraction   of  light   is    a   phenomenon    ob- 
served in  many  crystalline  transparent  bodies,  and  is  due  to 
their  peculiar  structure.    It  is  also  seen  in  bone,  shell,  horn, 
and  other  similar  substances.    The  beam  of  light  in  passing 
through  such  bodies  is  split  into  two  portions,  each  of  which 
gives  its  own  image  of  any  object  seen  through  the  doubly 
refracting  substance.     In  calcite,  carbonate  of  lime,  or  Ice- 
land-spar, this  phenomenon  is  beautifully  seen. 

A  sharp  line,  like  p  q,  fig.  66, 
when  seen  through  a  rhomb  of  calc- 
spar,  in  the  direction  of  the  ray  11  r, 
will  seem  to  be  double,  a  second 
parallel  line  m  n,  being  seen  at  a 
short  distance  from  it,  and  the  dot 
o  will  have  its  fellow  e.  In  this 
66m  case  the  light  is  represented  as  com- 

ing from  II  to  TJ  and,  passing  through  the  crystal,  it  is  split 
and  emerges  in  two  beams  at  e  and  o.  The  same  effect 
would  be  produced  if  the  light  fell  so  as  to  strike  any  part 
of  the  imaginary  plane  A  C  B  D,  which  divides  the  crystal 
diagonally  and  is  called  its  principal  section.  The  axis  or 
line  drawn  from  A  to  B  is  contained  in  this  plane.  But 
if  we  look  through  the  crystal  in  a  direction  parallel  to  this 
plane  (A  C  B  D)  there  is  only  simple  refraction,  and  only 
one  line  is  seen.  One  of  these  beams  is  called  the  ordinary 
and  the  other  the  extraordinary  ray.  In  the  case  of  crys- 
tallized minerals,  this  result  is  due  to  the  naturally  unequal 

What  lines  are  seen  in  the  spectrum?  70.  What  of  the  colors  of  na- 
tural bodies  ?  71.  What  is  double  refraction  ?  Describe  fig.  66.  What  is 
the  ordinary  ray?  Which  the  extraordinary?  What  relation  has  this 
phenomenon  to  crystallization? 


POLARIZATION. 


53 


elasticities  of  the  molecules  in  the  crystals — and  it  is  ob- 
served only  in  those  minerals  whose  molecules  are  ellipsoidal 
— and  is  wanting  in  those,  like  fluor-spar,  &c.,  which  belong 
to  the  cube  and  its  derivatives,  in  which  the  molecules  are 
spherical.  In  well  annealed  glass,  by  mechanical  pressure,  a 
sufficient  separation  of  the  two  rays  may  be  produced  to  cause 
color  by  interference,  though  not  enough  to  cause  two  images 

72.  Polarization. — The  light  which  has  passed  one  crys- 
tal of  Iceland-spar  by  extraordinary  refraction  is  no  longer 
affected  like  common  light.  If  we  attempt  to  pass  it  through 
another  crystal  of  the  same  substance,  there  will  be  no  fur- 
ther subdivision,  and  only  a  greater  separation  of  the  two 
beams.  This  peculiarity  of  the  extraordinary  ray  is  called 
polarization.  This  interesting  phenomenon  was  accident- 
ally discovered  in  1808  by  Malus,  while  looking  through 
a  doubly-refracting  prism  at  the  light  of  the  setting  sun, 
reflected  from  the  surface  of  a  glazed  door  standing  at  an 
angle  of  about  56°  45',  which  is  the  angle  at  which  glass 
polarizes  light  by  reflection. 

It  is  the  peculiarity  of  light  which  has  been  polarized 
that  it  will  no  longer  pass  through  certain  substances  which 
are  transparent  to  common  light.  Many  crystalline  sub- 
stances possess  the  power  of  polarizing  light.  The  mineral 
called  tourmaline  has  this  property  in  a  remarkable  degree. 
The  internal  structure  of  this  mineral  is  such  that  a  ray  of 
light  which  has  passed  through  a  thin  plate  of  it  cannot  puss 
through  a  second,  if  it  is  placed  in  a  position  at  right  angles 
with  the  first. 

For  example,  in 
the  annexed  figure 
(67)  we  have  two  R 
thin  plates  of  tour- 
maline placed  pa- 
rallel to  each  other 
in  the  same  direc- 
tion. A  ray  of  Fig.  67. 
light  passes  through 
both,  in  the  direction  of  R  R/,  and  apparently  suffers 
no  change :  if,  however,  these  plates  are  so  placed  as  to 
cross  each  other  at  right  angles,  as  in  fig.  68,  the  ray  of  light 


72.  What  is  polarization  ?   Who  discovered  this  phenomenon  ?    What  ia 
the  peculiarity  of  jiolarized  light?     Illustrate  this  from  tho  tourmaline. 


54 


LIGHT, 


is  totally  extinguished ;  and  two  such  points  may  be  found 
in  revolving  one  of  the  plates  about  the  ray  as  an  axis. 

73.     For  illustration,  we  may  suppose  the  structure  of 
this  mineral  to  be  such  that  a  ray  of  light 
can  pass  between  the  ranges  of  particles  in 
jne  direction  only,  as  a  flat  blade  may  pass 
-  between  the  wires  of  a  bird- 

\  cage,  fig.  69,  if  placed   pa- 

\  rallel  to  them;  but  will  be  Fig.  69. 

^  \  arrested  by  the  bars,  if  presented  at  right 

angles  to  the  wires. 

Light  is  polarized  in  many  ways,  as,  for 
example,  by  passing  through  a  bundle  of 
plates  of  thin  glass  or  of  mica,  as  in  fig.  70, 
by  reflection  from  the  surface  of  unsilvered 
glass,  of  a  polished  table  and  of  most  polished 
non-metallic   surfaces,   and  at  a  particular 
angle  for  each.    This  is  plane  polarized  light. 
74.  The  beautiful  phe- 
nomenon of  circular  and 
elliptic     polarization     is 
seen  in  many  crystalline 
bodies.    Plates  of  quartz, 
a  mineral  having  one  axis, 
show    the    prismatic    co- 
lors, when  viewed  by  po- 
larized light,  arranged  in 
circles  and  a  cross,  as  in  fig.  71; 
and    by    the   revolution    of    the 
plane  of  polarization  through  90°, 
the  colors  are  changed,  and  a  light 
cross  (fig.  71)  occupies  the  plane 
of  the  dark  one.     Nitre  gives  two 
axes  of  polarization,  which  in  the 
revolution  of  the  plane  show  the 
changes    seen   in   figures  73  and 
74.     Uniaxial  crystals  uniformly 
give   circular,  and    binaxial  ones 


Fig.  72. 


^  Fig.  73. 
elliptical  figures 


Fig.  74. 


When  is  the  ray  extinguished  ?  73.  How  is  this  phenomenon  explained 
in  reference  to  the  structure  of  the  crystal?  In  what  ways  is  light  po- 
larized? 74.  What  crystalline  bodies  give  circular,  and  what  elliptical 
polarization?  Illustrate  this  from  quartz  and  nitre. 


LIGHT. 


55 


75.  The  chemical  power  of  the  sun's  rays  is  seen  in  the 
blackening  of  chlorid  of  silver,  which  Scheele  long  ago  observed 
to  take  place  much  more  rapidly  in  the  violet  ray  than  in 
any  other  part  of   the  solar  spectrum.     It  was   afterward 
observed  by  Hitter  that  this  blackening  likewise  occurred 
beyond  the  violet  ray,  apparently  in  the  dark. 

The  researches  of  Neipce,  Daguerre,  and  others,  have 
greatly  enlarged  the  boundaries  of  our  knowledge  on  thia 
subject,  and  given  to  the  world  the  elegant  arts  of  the 
daguerreotype  and  photography.  The  darkening  of  metallic 
salts  by  light  is  owing  to  a  peculiar  class  of  rays  in  the 
spectrum,  called  by  Dr.  Herschel  the  chemical  rays,  which 
are  diffused  indeed  in  all  parts  of  the  spectrum,  but  which 
are  concentrated  with  more  power  beyond  the  violet.  This 
influence  has  also  been  variously  denominated  actinism, 
energia,  and  tithonicity. 

76.  The  accompanying  diagram  (fig.  75)  will  enable  the 
student  to  comprehend  this  subject  as  at  present  understood. 
From  A  to  B  we  have  the  solar 

spectrum,  with  the  colors  in  the 
same  order  as  already  described. 
The  cl  emical  power  is  greatest 
at  the  violet,  and  the  greatest 
heat  at  the  red  ray.  At  b 
another  red  ray  is  discovered, 
and  at  a  is  the  lavender  light. 
The  luminous  effects  are  shown  IXDIG0 
by  the  curved  line  C,  the  maxi-  BLUE,  '. . 
mum  of  light  being  found  at  GREEN,  . 
the  yellow  ray.  The  point  of 
greatest  heat  is  at  D,  beyond 
the  red  ray,  and  it  gradually 
declines  to  the  violet  end, 
where  it  is  entirely  wanting, 
the  other  limit  of  heat  being 
at  c.  The  chemical  powers 
are  greatest  about  E,  in  the 
limits  of  the  violet,  and  gra- 
dually extend  to  d,  where  they 
arc  lost.  They  disappear  also 


LAVENDER, 


EXTREME   RE1>, 

6:~i- 


Fig.  75. 


75.  What  is  the  chemical  power  of  the  sunbeam  ?    76.  Ulustrata  th« 
relations  of  the  chemical  and  other  rays,  from  fig.  75. 


56  PHOSPHORESCENCE. 

entirely  at  C ;  the  yellow  ray,  which  is  neutral  in  this  re- 
spect, attains  another  point  of  considerable  power  at  F,  in 
the  red  ray,  which  gives  its  own  color  to  photographic  pic- 
tures, and  disappears  entirely  at  e.  The  points  D,  C,  E,  there- 
fore represent  respectively  the  three  distinct  phenomena  of 
Heat,  Light,  and  Chemical  Power.  This  last  is. believed  to 
be  quite  independent  of  the  other  powers;  for  all  light  may 
be  removed  from  the  spectrum  by  passing  it  through  blue 
solutions,  and  yet  the  chemical  power  remains  unaltered. 

77.  It  will  readily  be  perceived  that  these  phenomena 
connected  with    the    sunbeam   exert   no   inconsiderable  or 
unimportant  influence  in  the  order  of  events,  whether  as 
connected  with  the  development  of  life  on  our  planet,  or 
with  those   great  physical    changes  which  depend  on   the 
calorific  and  magnetic  agencies  that  seem  inseparably  con- 
nected with  the  light  and  heat  of  the    sun.     Plants  can 
decompose    carbonic   acid   and   carry  on   the  functions    of 
nutrition  only  under  the  power  of  solar  light;  and  the  yellow 
ray  has  been  shown  by  Dr.  Draper  to  be  the  one  by  whose 
agency  this  change  is  effected  in  the  vegetable  kingdom. 

78.  Phosphorescence  is  a  property  possessed  by  some  bodies 
of  emitting  a  feeble  light,  often  at  ordinary  temperatures. 
The  diamond  and  some  other  substances,  after  being  exposed 
to  the  rays  of  the  sun,  will  emit  light  for  some  time  in  the 
dark.     Fluor-spar,  feld-spar,  and  some  other  minerals,  give 
out   a   fine  light  of  varied    hues,  when    gently  heated  or 
scratched.     Oyster-shells  which    have    been  calcined  with 
sulphur  and  exposed  to  the  sunlight,  will  shine  in  a  dark 
place  for  a  considerable  time  afterward,  and  even  an  electrical 
spark  will  renew  this  emanation.     The  glow-worm,  the  fire- 
fly, rotten  wood,  decaying  fish,  and  various  marine  animals 
possess  the  same  power,  although  in  these  cases  the  cause  is 
probably  different  from  that  which  excites  the  same  pheno- 
menon in  crystallized  bodies. 


77.  What  consequences  follow  the  phenomena  described?     78.  What  il 
phosphorescence  ? 


HEAT.  57 


III.  HEAT. 

Sources  and  Properties  of  Heat. 

79.  THE  phenomena  of  Heat,  or  Caloric,  are  eminenly 
interesting  to  the  chemical  student.     They  may  be  discussed 
under  two  general  divisions:  1.  The  Physical;  and,  2.  The 
Chemical.     Under  the  first  head  are  included  the  communi- 
cation of  heat,  by  radiation,  by  conduction,  and  convection; 
the  transmission  of   heat  by  various   substances,   and  the 
phenomena  of  expansion,  including  thermometers  and  pyro- 
meters ;  and  lastly,  specific  heat.     Under  the  second  head  are 
placed  the  changes  produced  by  heat  in  the  states  of  bodies ; 
for  example,  liquefaction  and  latent  heat  of  liquids,  vapor- 
ization   and  latent  heat  of  vapors,  liquefaction   of  gases, 
natural  evaporation  and  congelation,  density  of  vapors,  and 
so  forth. 

80.  The  sources  of  licat  are  chiefly  the  sun,  combustion, 
and  chemical  changes;  friction,  electricity,  vitality;  and, 
lastly,  terrestrial  radiation. 

Solar  heat,  as  is  well  known,  accompanies  the  sun's  light, 
and  it  unquestionably  results  from  the  intensely  high  tem- 
perature of  the  sun  itself.  It  is  believed  that  the  sun's 
rays  do  not  heat  the  regions  of  space,  and  the  earth's 
atmosphere  is  heated  almost  entirely  by  contact  with  the 
surface  of  the  heated  earth.  A  portion  of  the  sun's  heat  is 
however  taken  up  by  the  air  before  the  rays  reach  the  earth. 

Combustion  and  chemical  change,  including  vital  heat, 
are  sources  of  heat,  limited  by  the  quantity  of  matter  suffer- 
ing change,  and  to  the  time  in  which  the  change  takes  place. 
The  stores  of  fossil  fuel  laid  up  in  the  coal  formations  and 
the  vegetable  combustibles  now  on  the  earth's  surface  may 
be  considered  as  a  result  of  the  sun's  action  through  the 
powers  of  vegetable  life. 

Friction  causes  heat,  as  a  result  of  mechanical  motion. 
The  heat  of  friction  continues  as  long  as  the  mechanical 
power  required  to  produce  motion  is  maintained.  No 
change  of  state  or  loss  of  weight  is  necessarily  experienced 


79.  What  is  said  of  heat?  How  is  the  subject  discussed?  80.  What 
arc  the  sources  of  heat  ?  What  of  solar  heat  ?  What  of  combustion  ? 
What  of  friction? 


58  HEAT. 

ill  the  substances  employed.  Count  Rumford  showed  that 
in  the  boring  of  cannon  under  water,  the  heat  evolved  was 
so  considerable  as  to  bring  the  water,  in  a  short  time,  to  the 
boiling-point.  The  same  observer  succeeded  in  warming  a 
large  building  by  the  heat  evolved  from  the  constant  move- 
ment of  large  plates  of  cast-iron  upon  each  other.  Friction- 
heat  may  be  regarded  as  the  equivalent  of  the  motion  pro- 
ducing it.  The  heat  of  the  electrical  spark  and  of  the 
galvanic  current  will  be  considered  elsewhere. 

81.  Terrestrial  radiation  is  a    constant   source  of  heat, 
escaping  from  the  interior  of  the  earth,  and  has  doubtless 
some  effect  in  modifying  the  climate  of  our  globe.     Geolo- 
gists consider  it  proved  that  the  earth  has  cooled  to  its  pre- 
sent condition  from  a  state  of  intense  ignition,  and  that  this 
state  still  remains  in  the  interior,  at  no  very  considerable 
distance  from  the  surface.     All  deep  mines  and  Artesian 
wells  show  a  constant  and  progressive  increase  of  temperature 
in  going  down,  and  below  the  line  of  atmospheric  influence. 
The  Artesian  well  in  the  yard  of  the  great  Grenelle  slaughter- 
house, in  Paris,  is  2000  feet  deep,  and  the  water  rises  with  a 
temperature  of  85°  degrees  Fahrenheit.     At  Neusalzwerke, 
in  Westphalia,  is  a  well  2200  feet  deep,  and  its  water  has  a 
temperature  of  91°.     The  average  increase  of  temperature 
from  this  cause  is  estimated  to  be  1°8,  for  every  hundred 
feet  of  descent.     Assuming  this  ratio,  we  shall  have  at  two 
miles  the  boiling-point  of  water  ;  and  at  about  twenty-three 
miles,  or  only  Tg^th  of  the  earth's  radius,  there  must  be  a 
temperature  of  near  2200  degrees  of  Fahrenheit.     At  this 
heat,  cast-iron  melts,  and  trap,  basalt,  obsidian,  and  other 
rocks  are  perfectly  fluid.  The  geological  importance  of  these 
facts  is  self-evident ;  and  we  cannot  fail  to  remark  here  an 
efficient  cause  for  all  hot-springs. 

82.  Properties  of  Heat. — Heat  is  invisible  and  impon- 
derable.    It  proceeds,  like  light,  in  rays,  with  great  but 
hitherto  undetermined  velocity.     The  intensity  of  heat-rays 
varies  inversely  as  the   square    of  the    distance  .  from  the 
source  of  heat.     Rays  of  heat,  like  those  of  light,  may  be 
concentrated  from  a  metallic  mirror,  but  not  from  those  of 
glass,  as  this  substance  absorbs  heat  very  largely.     They  are 


81.  What  is  said  of  terrestrial  radiation?  What  is  determined  in  deep 
wells?  What  is  the  rate  of  increase  ?  At  what  depth  would  iron  rnelt? 
S2.  What  are  the  properties  of  heat?  How  is  it  like  light? 


COMMUNICATION    OF    HEAT.  59 

also  of  various  refrangibility,  and  capable  of  double  refrac- 
tion and  polarization.  Therefore,  they  move  in  waves  01 
undulations.  Heat  is  self-repellant,  as  two  bodies  heated  in 
vacuo  repel  each  other.  It  is  communicated  by  conduction 
and  by  convection  as  well  as  by  radiation.  It  is  variously 
absorbed  and  transmitted  by  various  substances,  and  pro- 
duces different  degrees  of  expansion,  varying  with  the  nature 
of  matter  affected.  Lastly,  it  determines  the  phenomena 
of  congelation,  liquefaction,  and  vaporization.  The  physio- 
logical sensation  of  cold  and  heat  experienced  in  our  per- 
sons is  not  to  be  confounded  with  the  physical  and  chemical 
phenomena  of  heat  now  to  be  discussed.  This  sensation  is, 
within  certain  limits,  entirely  relative.  For  example,  if  one 
hand  is  plunged  in  a  vessel  of  iced-water  and  the  other  into 
moderately  warm  water,  a  strong  contrast  is  evident  imme- 
diately ;  but  if  we  suddenly  transfer  both  hands  to  a  third 
vessel  of  water,  at  the  common  temperature,  our  sensations 
are  instantly  reversed.  The  third  vessel  is  warm  as  com- 
pared with  ice-water,  and  cold  compared  with  the  tepid 
water. 

Communication  of  Heat. 

83.  Heat  is  communicated  from  a  hot  body,  1.  By  radia- 
tion, or  transmission  of  rays  of  heat  in  all  directions ;  2. 
By  contact  of  the  atmosphere  conveying  it  away,  (convec- 
tion;) and,  3.  By  communication  to  the  substance  support- 
ing it,  (conduction.)     By  one  or  all  these  modes,  a  body 
placed  in  vacuo  or  in  the  air,  and  differing  in  temperature 
from  surrounding  bodies,  gradually  regains  the  equilibrium 
of  temperature.     If  hot,  it  loses,  and  surrounding  bodies 
gain ;  if  cold,  it  gains  at  the  expense  of  those  substances 
having  a  higher  temperature. 

84.  Radiation  takes  place  from  all  bodies  wherever  there 
is  a  disturbance  of  equilibrium,  but  in  very  various  degrees, 
according  to  the  nature  of  the  body  and  of  its  surface.     All 
bodies  have  a  specific   radiating  and    absorbing   power  in 
respect    to    heat.     To   these   the    retaining  and   reflecting 
powers  are   strictly  opposed.     Radiation    takes  place  in  a 
vacuum  more   easily  than  in  air,  and  is,  therefore,  quite 


What  is  said  of  the  sense  of  heat  and   cold  ?     Give  an  illustration. 
83.  How  is  boat  communicated  ?     84.  How  does  radiation  happen  ? 


60 


HEAT. 


Fig.  76. 


independent  of  any  conducting  medium. 
Rays  of  heat  may  be  concentrated  by  the 
parabolic  metallic  mirror.  All  rays  of 
heat  or  light  falling  on  this  form  of  mirror 
are  collected  at  F,  the  focus,  (fig.  76,)  and 
a  hot  body  placed  there  will  have  its  rays 
sent  forth  in  parallel  straight  lines,  as 
shown  in  the  figure.  A  second  and  similar 
mirror  may  be  so  placed  as  to  receive  and 
collect  in  a  focus  all  the  rays  proceeding 
from  any  body  in  the  focus  of  the  other, 
where  they  will  become  evident  by  their 
effect  on  the  thermometer.  If  the  hot  body  be  a  red-hot 
cannon-ball,  and  the  mirrors  are  carefully  adjusted,  so  as  to 
be  exactly  opposite  each  other  in  the  same  line,  the  accumu- 
lation of  heat  in  the  focus  of  the  second  mirror  is  such  as 
to  inflame  dry  tinder,  or  gunpowder,  even  at  many  feet 
distance. 

85.  This  striking  experiment  is  shown  by  the  conjugate 

mirrors,   arranged   as 
in  fig.  77.    Ice  placed 
in  the  focus  of  one  of 
the    mirrors  will    de- 
press a  thermometer 
in  the  other  focus, — 
not    because    cold    is 
^^^  radiated,  (as  cold  is  o 
£  mere    negation,)    but 

because  in  this  case  the  thermometer  is  the  hot  body  and 
parts  with  its  heat  to  fuse  the  ice.  A  thermometer  sus- 
pended midway  between  the  two  mirrors  is  not  affected.  A 
plate  of  glass  held  between  the  mirrors  will  cut  off  the  calorific 
rays — thus  proving  a  difference  of  penetrating  power  be- 
tween the  rays  of  heat  and  of  those  of  light.  As  soon  aa 
the  screen  is  raised  the  phosphorus  in  the  focus  is  inflamed. 

86.  Radiation  and  Absorption  of  heat  are  exactly  equal 
to  each  other  in  a  given  '  surface,  but,  as   before    stated, 
the  nature  of  the  substance  and  of  the  surface  have  much 
influence  in  these  respects.    All  black  and  dull  surfaces  ab- 
sorb heat  very  rapidly  when  exposed  to  its  action,  and  part 


How  does  a  metallic  mirror  affect  heat?     85.  Describe  the  experiment 
in  fig.  77.     86.  What  of  absorption?     Hovr  does  color  affect  it? 


CONDUCTION   OF    HEAT  61 

with  it  again  by  secondary  radiation.  The  sun  shining  on 
a  person  dressed  in  black  is  felt  with  much  more  power  than 
if  he  were  dressed  in  white.  The  former  color  rapidly 
absorbs  heat,  while  from  the  latter  a  considerable  part  of  it 
is  reflected.  The  color  of  bodies  has,  however,  nothing  to 
do  with  their  radiating  powers,  and  one  colored  cloth  is  as 
warm  in  winter  as  another,  as  regards  the  emission  of  heat. 
(Bache.) 

If  the  radiating  power  of  a  surface  covered  with  lamp- 
black be  assumed  as  100,  that  of  a  surface  covered  with 
Indian  ink  will  be  88,  with  ice  85,  with  graphite  75,  with 
dull  lead  45,  with  polished  lead  19,  with  polished  iron  15, 
with  polished  tin,  copper,  silver,  or  gold,  12.  (Leslie.) 
Hence  the  polished  metallic  vessel,  which  is  so  well  adapted 
to  retain  the  heat  of  boiling  water,  is  the  very  worst  vessel 
in  which  to  attempt  to  boil  it.  The  sooty  surface  next  the 
fire,  however,  transmits  heat  with  the  greatest  rapidity.  In 
the  experiment  with  the  mirrors  just  described,  the  polished 
surfaces  remain  cool,  reflecting  nearly  all  the  heat  which 
falls  upon  them.  A  glass  mirror  in  the  same  experiment 
would  be  useless,  as  glass  absorbs  nearly  all  the  heat,  of  low 
intensity,  which  falls  upon  it. 

87.  The  formation  of  dew  is  owing  to  radiation,  cooling 
the  surface  of  the  earth  so  rapidly,  that  the  moisture  of  the 
air,  which  is  always  abundant  in  summer,  is  condensed  upon 
it :  as  we  see  it  on  the  outside  of  a  tumbler  of  iced-water  in 
a  hot  day.     Radiation  takes  place  more  rapidly  from  the 
surface  of  grass  and  vegetation  than  from  dry  stones  or 
dusty  roads  :  for  this  reason,  plants  receive  abundant  dew, 
while  the  barren  sand  has  none. 

88.  Conduction  of  heat. — A  metallic  bar  placed  by  one 
end  in  the  fire,  slowly  becomes  hot,  the  heat  being  trans- 
mitted  by  conduction  from  particle  to  particle.     Each  so- 
lid  has  its  own    peculiar   rate    of  conducting   heat,    but 
in   all  it  is  a  progressive  operation,  the  heat  seeming  to 
travel  with  greater  or  less  rapidity,  according  to  the  nature 
of  the  solid.     If  we  hold  a  pipe-stem  or  glass  rod  in  the 
flame  of  a  spirit-lamp  or  candle,  we  can  heat  it  to  redness 
within  an  inch  of  our  fingers  without  inconvenience ;  but  a 
wire  of  silver  or  copper  held  in  the  same  manner  soon  be- 


Give  some  results  of  radiation  from  different  substances.      87.  How  U 
dew  formed  ?    88.  What  is  conduction  ?    Why  does  it  fall  on  plants  ? 


62  HEAT. 

comes  too  hot  to  hold.  This  is  owing  to  an  inherent  dif- 
ference in  these  solids,  which  we  call  conducting  power.  The 
.  ]  progress  of  conducted 

6  heat  in  a  solid  is  easi- 
ly  shown,  as  in  fig.  78, 
representing  a  rod  of 

copper,  to  which  are  stuck  by  wax  several  marbles  at  equal 
distances ;  one  end  is  held  over  a  lamp,  and  the  marbles 
drop  off,  one  by  one,  as  the  heat  melts  the  wax;  that 
nearest  the  lamp  falling  first,  and  so  on.  If  the  rod  is  of 
copper,  they  all  fall  off  very  soon  ;  but  if  a  rod  of  lead  or 
platinum  is  used,  the  heat  is  conveyed  much  more  slowly. 
Little  cones  of  various  metals  and  other  substances  may  be 
tipped  with  wax  or  bits  of  phosphorus,  as 
shown  in  fig.  79,  and  placed  on  a  hot  surface. 
The  wax  will  melt,  or  the  phosphorus  inflame, 
at  different  times,  according  to  the  conducting 
°'  power  of  the  various  solids.  A  screen  is 

needed  to  cut  off  the  radiant  heat,  which  would  otherwise  in- 
flame the  phosphorus  prematurely.  Accurate  experiments 
have  been  made,  which  have  enabled  us  to  arrange  most  so- 
lids in  a  table  showing  their  conducting  powers.  The  metals, 
as  a  class,  are  good  conductors,  while  wood,  charcoal,  fire-clay, 
and  similar  bodies  are  bad  ones.  Thus  gold  is  the  best  con- 
ductor, and  may  be  represented  by  the  number  1000 ;  then 
marble  will  be  23-5,  porcelain  12,  and  fire-clay  11.  Metals, 
compared  with  each  other,  are  very  different  in  conducting 
power.  Thus — 


Gold 1000 

Silver 973 

Copper 898 

Platinum 381 


Iron 375 

Zinc 363 

Tin 304 

Lead  ...  ,...180 


89.  Vibrations  occur  in  masses  of  metals  and  other  sub- 
stances when  conducting  heat,  which  seem  to  indicate  the 
production  of  waves  or  undulations  among  the  particles. 
Mr.  Trevellyan  has  remarked  that  if  a  mass  of  warm  brass 
is  placed  on  a  support  of  cold  lead,  the  rounded  surface  of 


What  is  its  rate  in  different  substances  ?  89.  How  is  an  undulation 
proved  to  exist  in  heated  bodies  ?  Mention  Trevellyan  and  Page's  ex- 
periments. 


CONDUCTION   OF   HEAT.  63 

the  brass  resting  on  the  flat  surface  of  the  lead,  the  brass 
bar  is  thrown  into  a  series  of  vibrations,  accompanied  by 
a  distinct  sound  and  a  rocking  motion,  of  the  brass,  until 
equilibrium  is  restored.  Dr.  Page  has  shown  that  a  current 
of  galvanic  electricity  passed  through  a  similar  apparatus 
produces  the  same  results.  Fig. 
80  shows  Page's  apparatus,  in 
which  a  feeble  current  of  electri- 
city produces  a  rocking  motion  of 
the  metallic  masses  resting  on  the 
bars  of  brass.  The  best  effects  are 
Fig.  80.  produced  between  good  and  bad 

conductors  of  heat,  the  former  being  the  hot  bodies. 

90.  Heat  is  conducted  in  crystallized  bodies,  in  curves 
springing  from  the  sources  of  heat.    In  plates  of  homoge- 
neous substances  these  curves  are  circles ;  in  those  of  a  crys- 
talline texture,  belonging  to  the  rhombohedral  system,  the 
curves  are  ellipses  of  very  exact  form,  whose  longer  axes  are 
in  the  direction  of  the  major  crystalline  axis — proving  the 
conducting  power  of  such  bodies  to  be  greatest  in  that  direc- 
tion.    The  mode  of  experimenting  in  such  cases  is  to  cover 
the  surface  of  the  crystalline  plate  with  wax,  heat  very  gra- 
dually, and  watch  the  lines  of  fusion  on  the  surface. 

91.  The  sense  of  touch  gives  us  a  good  idea  of  the  dif- 
ferent conducting  power  of  various  solids.     All  the  articles 
in  an  apartment  have  nearly  the  same  temperature ;  but  if 
we  lay  our  hand  on  a  wooden  table,  the  sensation  is  very  dif- 
ferent from  that  which  we  feel  on  touching    the   marble 
mantel  or  the   metal  door-knob.      The  carpet  will  give  us 
still  a  different  sensation.    The  marble  feels  cold,  because  it 
rapidly  conducts  away  the  heat  from   the  hand ;   while  the 
carpet,  being  a  very  bad  conductor,  retains  and  accumulates 
the  heat,  and  thus  feels  warm.    Clothing  is  not  itself  warm, 
but,  being  a  bad  conductor,  retains  the  heat  of  the  body.  A 
film  of  confined  air,  is  one  of  the  worst  conductors;  loose 
clothes  are  therefore  warmer  than  those  which  fit  closely. 
For  the  same  reason,  porous  bodies,  like  charcoal,  are  bad 
conductors ;  and  a  wooden  handle  enables  us  to  manage  hot 
bodies  with  ease. 

92.  The  conducting  power  of  fluids  is  very  small.     A 


90.  How  is  heat  conducted  in  crystals?     91.  What  does  touch  inform 
us  of  ?     92.  What  of  the  conducting  power  of  fluids  ? 


64 


HEAT, 


simple  and  instructive  experiment  will  prove  this  satis- 
factorily. A  glass,  like  that  in  fig.  SI, 
is  filled  nearly  to  the  brim  with  water. 
A  thermometer-tube,  with  a  large  ball, 
is  so  arranged  within  it  that  the  ball 
is  just  covered  with  the  water :  the 
stem  passes  out  at  the  bottom  through 
a  tight  cork,  and  has  a  little  colored 
fluid,  L,  in  it,  which  will,  of  course, 
move  with  any  change  of  bulk  in  the 
air  contained  in  the  ball. 

Thus  arranged,  a  pointer  I  marks 
exactly  the  position  of  one  of  the  drops 
of  enclosed  fluid,  when  a  little  ether  is 
poured  on  the  surface  of  the  water, 
and  set  on  fire.  The  flame  is  intensely 
hot,  and  rests  on  the  surface  of  the 
water  j  the  column  of  fluid  at  I  is, 
however,  unmoved,  which  would  not 
be  the  case  if  any  sensible  quantity  of 
heat  had  been  imparted  to  the  water. 
The  warmth  of  the  hand  touching  the 
ball  will  at  once  move  the  fluid  at  I, 
by  expanding  the  air  within.  By  heat- 
ing a  vessel  of  water  on  the  top,  then, 
,  we  should  never  succeed  in  creating  any 
thing  more  than  a  superficial  elevation 
of  temperature  :  at  a  small  depth  the 
Fig.  81.  water  would  remain  cold.  Liquids  do 

possess  a  very  low  conducting  power,  contrary  to  the  opinion 
of  Count  llumford,  and  heat  appears  to  be  propagated  in 
them  by  the  same  law  as  in  solids,  when  care  is  taken  to 
avoid  the  production  of  currents. 

93.  The  conducting  power  of  gases  is  also  very  small. 
Heat  travels  with  extreme  slowness  through  a  confined 
portion  of  air.  This  is  a  very  different  thing  from  the  con- 
vection of  heat  in  gases,  which  we  will  presently  explain. 
Double  windows  and  doors,  and  furring  (so  called)  of  plas- 
tered walls,  afford  excellent  illustrations  of  the  slow  con- 
duction of  heat  through  confined  air.  We  have  no  proof 
that  heat  can  be  conducted  in  any  degree  by  gases  and  va» 


Explain  the  experiment,  fig.  81.   What  of  the  conducting  power  of  gases? 


CONVECTION   OF    HEAT. 


65 


pors.  To  illustrate  the  relative  conducting  powers  of  solids, 
fluids,  and  gases :  if  we  touch  a  rod  of  metal  heated  to  120°, 
we  shall  be  severely  burned ;  water  at  150°  will  not  scald, 
if  we  keep  the  hand  still,  and  the  heat  is  gradually  raised ; 
while  air  at  300°  has  been  often  endured  without  injury. 
The  oven-girls  of  Germany,  clad  in  thick  socks  of  woollen, 
to  protect  the  feet,  enter  ovens  without  inconvenience  whero 
all  kinds  of  culinary  operations  are  going  on,  at  a  tempera- 
ture above  300° ;  although  the  touch  of  any  metallic  article 
while  there  would  severely  burn  them. 

94.  Convection  of  heat  is  its  transportation,  as  in  liquids 
and  gases,  by  the  power  of  currents. 

Heat  applied  from  beneath  to  a  vessel 
containing  water,  warms  the  layer  or 
film  of  particles  in  contact  with  the 
vessel.  These  expand  with  the  heat, 
and  consequently,  becoming  lighter, 
rise,  and  colder  particles  supply  their 
place,  which  also  rise  in  turn,  and 
so  the  whole  contents  of  the  vessel 
come  in  quick  succession  into  con- 
tact with  the  source  of  heat,  and 
convey  it  through  the  mass.  This 
is  well  illustrated  in  fig.  82,  which 
shows  how  water  acts  in  a  vessel  of 
glass,  when  heated  at  a  point  be- 
neath by  a  spirit-lamp.  Each  par- 
ticle in  turn  comes  under  the  in- 
fluence of  heat,  because  of  the  per- 
fect mobility  of  the  fluid.  A  series 
of  such  currents  exists  in  every 
vessel  in  which  water  is  boiled,  and 
they  are  rendered  more  evident  by  throwing  into  it  a  few 
grains  of  some  solid  (like  amber)  so  nearly  of  the  same 
gravity  of  water  that  it  will  rise  and  fall  with  the  currents. 

95.  In  the  air,  and  in  all  gases  and  vapors,  the  same 
thing  happens.    The  earth  is  heated  by  the  sun's  rays,  and 
the  film  of  air  resting  on  the  heated  surface  rises,  to  be  re- 
placed by  cold  air.     The  rarefied  air  may  be  easily  seen,  on 
a  hot  day,  rising  from  the  surface  of  the  earth,  being  made 


Fig.  82. 


94,  What  is  convection  ?  Illustrate  it  in  water.   95.  How  is  heat  distri 
outed  in  air. 

5 


66  HEAT. 

visible  \>'j  its  different  refractive  power.  Hence  arise  many 
aerial  currents  and  winds.  The  currents  of  the  ocean  aro 
also  influenced  by  the  same  cause. 

Transmission  of  Seat. 

96.  Light  passes  through  all  transparent  bodies  alike, 
from  what  source  soever  it  may  come.     The  rays  of  heat 
from  the  sun  also,  like  the  rays  of  light  from  the  same  lu- 
minary, pass   through   transparent    substances  with    little 
change    or  loss.     Radiant   heat,  however,  from  terrestrial 
sources,  whether  luminous  or  not,  is  in  a  great  measure  ar- 
rested by  many  transparent  substances.   If  the  sun's  rays  be 
concentrated  by  a  metallic  mirror,  the  heat  accompanying 
them  is  so  intense  at  the  focus  as  to  fuse  copper  and  silver  with 
ease.     A  pane  of  colorless  window-glass  interposed  between 
the  mirror  and  the  fpcus,  will  not  stop  any  considerable  part 
of  the  heat.     If  the  same  mirror  is  presented  to  any  other 
source  of  heat,  however,  (as,  for  example,  to  the  red-hot  ball, 
85,)  the  glass  plate  will  stop  nearly  all  the  heat,  although 
the  light  is  undiminished.    We  thus  distinguish  two  sorts  of 
calorific  rays,  which  are  sometimes  called  Solar  and  Culinary 
Heat;  and  we  discover  that  substances  transparent  to  light 
are  not,  so  to  speak,  transparent  to  heat  in  a  like  degree. 
This  property  is  distinguished  from  transparency  by  the  term 
Diathermancy,  (meaning  the  easy  transmission  of  heat.)     It 
appears  that  many  substances  are  eminently  diathermous, 
which  are  almost  opake  to  light;    like  smoky  quartz,  for 
example.     The  temperature  of  the  source  of  heat  has  the 
greatest  influence  on  the  number  of  rays  of  heat  which  are 
transmitted  by  a  given  screen ;  as  in  the  case  of  the  glass 
plate,  which  permits  nearly  all  the  sun's  rays  to  pass,  but 
arrests  over  65  per  cent,  of  the  rays  from  a  lamp-flame. 

97.  Our  knowledge  on  this  subject  has  been  derived  almost 
entirely  from  the  researches  of  M.  Melloni,  of  Naples.     This 
philosopher,  by  the  use  of  a  peculiar  apparatus,  called  the 
thermo-electric  pile,  was  able  to  detect  differences  of  tempera- 
ture  altogether  inappreciable  by  common  thermometers.  This 
instrument  is  an  arrangement  of  little  bars  of  the  two  metals, 


96.   Distinguish  transmission  of  heat  from  that  Qf  light.     What  ij 
diathermancy  ?    What  was  Melloni's  research  ? 


TRANSMISSION   OP   HEAT. 


67 


Fig.  83. 


antimony  and  bismuth,  about  fifty  of  which  are  sol- 
dered together  by  their  alternate  ends,  the  whole 
being,  with  its  case,  not  more  than  2£  inches  long, 
by  £  to  i  of  an  inch  in  diameter.  The  least  differ- 
ence of  heat  between  the  opposite  ends  of  this  little 
battery  will  produce  an  electrical  current  capable  of  influenc- 
ing a  magnetic  needle  in  an  instrument  called  a  galvanome- 
ter, (§202.)  The  needle  of  the  galvanometer  will  move  in  exact 
accordance  to  the  intensity  of  the  heat.  This  is  so  delicate 
an  instrument,  that  the  radiant  heat  of  the  hand  held  near 
the  battery  will  cause  the  needle  to  move  some  10°  over  its 
graduated  circle.  In  fig.  84,  a  is  the  source  of  heat,  (an  oil- 


Fig.  84. 

lamp  in  this  case,)  &  a  screen  having  a  hole  to  admit  the 
passage  of  a  bundle  of  rays;  c  is  the  substance  on  which  the 
heat  is  to  fall  ;  d  the  thermo-multiplier,  or  battery,  which  is  to 
receive  the  rays  after  they  have  passed  through  the  substance 
c.  Two  wires  connect  the  opposite  members  of  this  battery 
with  the  galvanometer  e,  which,  for  steadiness,  is  placed  on 
a  bracket  attached  to  the  wall.  Thus  arranged,  and  with 
various  delicate  aids  which  we  cannot  here  explain,  a  vast 
number  of  most  instructive  experiments  have  been  made  on 
radiant  heat  from  different  sources,  and  its  effect  ascertained 
on  various  substances.  Four  different  sources  of  heat  were 
employed  :  1.  The  naked  flame  of  an  oil-lamp  ;  2.  A  coil  of 
platinum  wire  heated  to  redness  by  an  alcohol-lamp;  3.  A 
surface  of  blackened  copper  heated  to  734°;  and,  4.  The 
game  heated  to  212°  by  boiling  water.  The  first  two  of 
these  are  luminous  sources  of  heat,  the  last  two  non-luminous. 
98.  As  already  stated,  the  temperature  of  the  source 


97.  What  are  Melloni's  researches  ?    Describe  the  arrangement  in  figs. 
83  and  Si. 


«8 


HEAT. 


greatly  influences  the  number  of  rays  transmitted.  That 
which  has  passed  through  one  plate  of  rock-salt  has  less 
liability  to  be  arrested  by  a  second;  still  less  by  a  third,  and 
so  on. 

The  following  table  will  show  a  few  of  the  principal  re- 
sults : — 


Names  of  interposed  substances,  common  thickness, 
0.102  inch. 

Transmission  of  100 
rays  of  heat  from 

A 

1 

92 
36 
39 
38 
37 
9 
8 
6 

ll 

I'-s 

92 
28 
24 
28 
28 
2 
0 
0 

Copper  at 
734°. 

F 

92 
6 
6 
6 
6 
0 
0 
0 

92 
0 
0 
0 
0 
0 
0 
0 

Iceland-spar  .      ...          

Plate-glass  

Rock-crystal  

Alum,  transparent  

Ice,  pure  and  transparent  

Thus  it  appears  that  rock-salt  is  the  only  substance  which 
permits  an  equal  amount  of  heat  from  all  sources  to  pass. 
In  other  cases,  the  number  of  rays  passing  seem  proportioned 
to  the  intensity  of  the  source.  M.  Melloni  has  called  rock- 
salt  the  glass  of  heat,  as  it  permits  heat  to  pass  with  the  same 
ease  that  glass  does  light.  It  is  supposed  that  the  difference 
found  by  experiment  in  the  diathermancy  of  bodies  is  owing 
to  a  peculiar  relation  which  the  various  rays  of  heat  sustain 
to  these  bodies,  analogous  to  that  difference  in  the  rays  of 
light  which  we  call  color.  Thus  all  other  bodies,  except  salt, 
act  on  heat  as  colored  glasses  act  on  light,  entirely  absorbing 
some  of  the  colors,  and  allowing  others  to  pass.  In  this 
view,  rock-salt  may  be  said  to  be  colorless  as  respects  heat, 
while  alum  and  ice  are  in  the  same  sense  almost  back. 
Opake  bodies,  like  wood  and  metals,  entirely  prevent  the 
transmission  of  heat ;  but  dark-colored  quartz  crystal  is  seen, 
by  the  table,  to  differ  only  1  from  white  crystal,  and  even 
perfectly  black  glass  does  not  entirely  stop  all  heat. 

99.  By  cutting  rock-salt  into  prisms  and  lenses,  the  heat 
from  radiant  bodies  may  be  reflected,  refracted,  and  concen- 


98.  What  substance  transmits  heat  most  readily?     Which  least  so? 
What  is  rock-salt  called  ?     99.  How  is  heat  polarized,  «fcc.  ? 


EXPANSION.  69 

trated.  like  light,  and  doubly  refracting  minerals,  like  Ice- 
land-spar, will  polarize  it. 

Expansion  of  Bodies  lyy  Heat. 

100.  All  bodies  expand  with  an  increase  of  heat,  and 
diminish  with  its  loss.  The  expansion  of  a  solid  may  be 
shown  by  a  bar  of  metal  which,  as  in 
the  fig.  85,  is  provided  with  a  handle, 
which  at  ordinary  temperatures  ex- 
actly fits  the  gauge.  On  heating  this 
over  a  spirit-lamp,  or  by  plunging  it 
into  hot  water,  it  will  be  so  much 
expanded  in  all  its  dimensions  as  no 
longer  to  enter  the  gauge.  On  cool- 
ing it  with  ice,  it  will  again  not  only 
enter  freely,  but  with  room  to  spare. 
The  same  fact  is  shown  by  a  ball,  to 
which,  when  cold,  a  ring  with  a  han- 
dle will  exactly  fit;  but  on  heating 
the  ball,  the  ring  will  no  longer  encircle  it. 

The  expansion  of  a  fluid  may  be  shown  by  filling  the  bulb , 
of  a  large  tube  (fig.  86)  with  coloured  water  to  a  mark  on 
the  stem.     On  plunging  the  bulb  into 
hot  water,  the  fluid  is  seen  to  rise  rapidly 
in  the  stem.     If  it  be  cooled  by  a  mix- 
ture of  ice  and  water,  it  is  seen  to  sink 
considerably  below  the  line.    A  similar 
bulb  (fig.  87)  filled  with  air,  and  hav- 
ing its  lower  end  under  water,  is  ar- 
ranged as  in  the  figure,  to  show  the  — [ 
expansion  of  air  by  heat.    The  warmth 
of  the  hand  applied  to  the  naked  ball 
will  be  sufficient  to  cause  bubbles  of  air 
to  escape  from  the  open  end  through 
the  water ;  and  on  removing  the  hand, 
the  contraction  of  the  air  in  the  ball,  FiS-  86> 
from  the  cooling  of  the  surface,  will  cause  a  rise  of  the  fluid 
in  the  stem,  corresponding  to  the  volume  of  air  expelled,  as 


100.  What  is  expansion  ?    Illustrate  it  for  a  solid.    For  a  liquid.    Foi 
a  gas. 


70 


HEAT. 


shown  in  the  figure.  The  slightest  change  of  temperature 
will  cause  this  column  of  fluid  to  move,  as  the  air  expands 
or  contracts.  In  fact,  it  is  the  old  air-thermometer. 

101.  Expansion  of  JSolids. — Expansion  by  heat  varies 
greatly:  1.  According  to  the  nature  of  the  substance ;  and, 
2.  Not  in  degree  only,  but  also  in  the  law  which  it  follows. 
In  solids,  between  the  freezing  and  boiling  of  water,  the  rate 
of  expansion  in  the  same  solid  is  equal  for  each  additional 
degree.  In  experiments  on  this  subject,  rods  of  equal  length 
are  used,  composed  of  the  various  subjects  of  experiment, 
whose  expansion  in  length  is  accurately  measured. 

In  fig.  88,  the 
rod  t  is  confined 
by  a,  so  that  its 
free  end  bears 
against  b.  Heat- 
ed by  an  alcohol 
lamp,  or  other 

_LLL«  LLO7  a  »  S       source  of  heat,  it 
expands  and  car- 
ries forward  the 
Fig.  88.  index  g  over  the 

graduated  arc  c.  On  cooling,  it  contracts,  and  the  spring  a 
moves  the  index  back  again  to  the  starting  point.  This 
linear  expansion,  multiplied  by  3,  gives  the  expansion  in 
volume  very  nearly.  Thus,  for  example,  in  the  following 
solids,  when  heated  from  32°  to  212°  Fahrenheit,  the  ex- 
pansion is — • 


In  Length. 


In  Bulk. 


339  parl 
349 

s  of  zinc               =    340     c 
lead               =    350 

r    11  2  parts  =  113 
116      "    =117 

523 

silver            =    524 

174      «    =  175 

583 
643 
810 

copper           =    584 
gold               =     644 
iron                =    811 

194      "    =  195 
217      "    =  218 
270      "    =271 

921 
1006 
1113 
2831 

antimony      =    922 
platinum       =1007 
white  glass  =  1114 
black  marble  =2832      < 

307      "    =308 
335      "    =  336 
371      "    =372 
«      943      "    =944 

102.  The  expansion  of  fluids  is  ether  apparent  or  absolute, 
according  as  the  dilatation  of  the  containing  vessel  is  or  is  not 


101.  What  is  the  rate  of  expansion  in  solids  ? 
examples  from  table,  in  length  and  bulk. 


Describe  fig.  88.     Give 


EXPANSION. 


71 


taken  into  account.  This  fact  may  be 
illustrated  in  the  annexed  apparatus,  (fig. 
89,)  where  a  tube  of  glass  is  bent  twice  at 
right  angles,  the  open  ends  a  and  b  upper- 
most; a  larger  tube  surrounds  each,  leaving 
two  cells,  in  which  water  of  different  tem- 
peratures may  be  poured.  The  inner  tube 
is  filled,  for  example,  with  colored  water, 
of  the  ordinary  temperature,  to  the  level  P; 
hot  water  is  now  poured  into  the  outer  cell 
of  6,  when  an  immediate  elevation  of  level 
in  the  colored  fluid  is  seen  to  m.  This  is 
on  the  principle  that  the  heights  of  columns 
of  liquids  in  equilibrium  are  inverse  to  their 
densities.  In  this  manner  it  has  been  de- 
termined that  in  heating  from  33°  to  212°, 
9  measures  of  alcohol  becomes  10 ;  of  water, 
23  measures  becomes  24 ;  and  of  mercury, 
55  measures  becomes  56.  Thus  it  happens  that  in  the  com- 
mon changes  of  the  seasons  the  bulk  of  spirits  varies  about 
5  per  centum.  It  has  been  determined,  also,  that  liquids 
are  progressively  more  expansible  at  higher  than  at  lower 
temperatures.  The  liquefied  gases  illustrate  this  law  in  a 
remarkable  manner,  for  fluid  carbonic  acid,  as  observed  by 
M.  Thilorier,  has  a  dilatation  four  times  greater  than  is  ob- 
served in  common  air  at  the  same  temperatures.  The  law 
of  expansion  in  liquids  is  not  yet  well  made  out. 

103.  Unequal  Expansion  of  Water. — The  general  law  of 
expansion  for  nearly  all  solids  and  fluids,  especially  within 
the  limits  of  the  freezing  and  boiling  points  of  water,  is, 
that  each  solid  or  fluid  expands,  or  contracts,  an  equal  amount 
for  every  like  increase,  and  reduction  of,  temperature,  each 
body  having  its  own  rate  of  dilatation.  There  are,  how- 
ever, some  exceptions  to  this  law,  of  which  water  offers  a 
remarkable  example.  As  the  comfort,  and  even  habitability 
of  our  globe,  are  in  a  great  degree  dependent  on  this  excep- 
tion to  the  ordinary  laws  of  nature,  it  is  worthy  of  special 
notice. 

If  we  fill  a  large  thermometer-tube  or  bulbed  glass  (fig.  90) 
with  water,  and  place  it  in  a  freezing  mixture,  where  wo 


102.  Describe  the  apparatus  fig.  89.    "What  is  the  expansion  of  water? 
Of  alcohol?     103.  What  inequality  in  the  expansion  of  water? 


72  HEAT. 

can  observe  the  fall  of  the  temperature  by  the 
thermometer,  we  shall  see  the  column  descend 
regularly  with  the  temperature,  until  it  reaches 
39 -°1  F.,  when  the  contrary  effect  will  take  place : 
the  water  then  begins  suddenly  to  rise  in  the  tube, 
by  a  regular  expansion,  until  the  temperature 
falls  to  32°,  when  so  sudden  a  dilatation  takes 
place  as  to  throw  the  water  in  a  jet  from  the  open 
orifice.  If,  on  the  other  hand,  we  heat  water  in 
such  an  apparatus,  commencing  at  32°,  we  shall 
find  that,  until  the  temperature  rises  to  40°,  the 
fluid,  in  place  of  expanding  as  we  might  expect, 
Fig.  90.  will  actually  contract.  Water  has,  therefore, 
its  greatest  density  at  39°  -5,  and  its  density  is 
the  same  for  equal  temperatures  above  and  below  this  point ; 
thus  we  shall  find  it  having  a  similar  density  at  34°  and  45°. 
104.  Beneficial  Results. — Let  us  now  observe  what  useful 
end  this  curious  irregularity  in  the  expansion  of  water  sub- 
serves. When  winter  approaches,  the  lakes  and  rivers,  by 
the  contact  of  the  cold  air,  begin  to  lose  their  heat  on  the 
surface;  the  colder  water,  being  more  dense,  falls  to  the  bot- 
tom, and  its  place  is  supplied  by  warmer  water  rising  from 
below.  A  system  of  circulation  is  thus  set  in  motion,  and 
its  tendency,  if  the  mass  of  water  is  not  too  large,  is  to  reduce 
the  whole  gradually  to  the  same  temperature  throughout. 
When,  however,  the  water  has  cooled  to  39° -5,  this  circula- 
tion is  arrested  by  the  operation  of  the  law  just  explained ; 
below  this  point  the  water  no  longer  contracts  by  cooling, 
and  of  course  does  not  sink ;  but  on  the  contrary  expanding, 
as  before  explained,  it  becomes  relatively  lighter,  and  remains 
on  the  surface :  the  temperature  of  this  layer  or  upper  stratum 
gradually  falls,  until  the  freezing  point  is  reached,  and  a 
film  of  ice  is  formed.  But  as  ice  is  a  very  bad  conductor, 
the  heat  now  escapes  with  extreme  slowness;  all  currents 
tending  to  convey  away  the  cooler  parts  of  the  water  are 
arrested,  and  the  thickness  of  the  ice  can  increase  only  by 
the  slow  conduction  through  the  film  already  formed  :  the 
consequence  is,  that  our  most  severe  winters  fail  to  make  ice 
of  any  great  thickness.  Other  causes,  also,  which  we  shall 


What  is  its  maximum  density  ?  104.  What  beneficial  result  follows  ? 
Why  is  freezing  a  slow  process  ?  Describe  the  mode  of  freezing  of  lake* 
aud  rivers. 


EXPANSION.  7iJ 

presently  explain,  co-operate  at  all  times  to  render  the  freez- 
ing of  water  a  very  slow  process.  We  cannot  fail  to  be  im- 
pressed by  the  wisdom  of  that  Power,  which  not  only  frames 
great  general  laws  for  the  government  of  matter,  but  also 
makes  exceptions  to  them,  when  the  welfare  of  His  creatures 
requires  them. 

105.  The  expansion  of  all  gases  and  vapours  is  the  same 
for  an  equal  degree  of  heat,  and  equal  increments  of  heat 
produce  equal  amounts  of  expansion.    The  rate  of  expansion 
amounts  to  4-^th  part  of  the  volume  of  the  gas  at  0Q  for 
each  degree  of  Fahrenheit's  scale,  or  between  32°  and  212° 
to  0-366,  or  more  than  £  of  the  initial  volume  of  the  gas. 

When  gases  are  near  the  point  of  compression  at  which 
they  become  liquid,  this  law  becomes  irregular,  and  is  not 
strictly  true  for  all  gases ;  but  the  departures  from  the  law 
are  so  small  that  we  need  not  mention  them  here. 

106.  Practical  application  of  the  laws  of  expansion  in 
solids  are  frequently  made  with  great  advantage  in  the  arts. 
The  rivets  which  hold  together  the  plates  of  iron  in  steam- 
boilers  are  put  in  and  secured  while  red-hot,  and  on  cooling 
draw  together  the  opposite  edges  of  the  plates  with  great 
power.     The  wheelwright  secures  the  parts  of  a  carriage- 
wheel  by  a  red-hot  tire,  or  belt  of  iron,  which  being  quickly 
quenched,  before  it  chars  the  wood,  binds  the  whole  fabric 
together  with  wonderful  firmness.     The  walls  of  the  Con- 
servatory of  Arts,  in  Paris,  after  they  had  bulged  badly,  were 
safely  drawn  into  a  vertical  position,  by  the  alternate  con- 
traction and  expansion  of  large  rods  of  iron  passed  across  it, 
and  so  secured  by  screw-nuts  and  heated  by  Argand  lamps 
as  to  draw  the  walls  inward.     Towers  of  churches  and  other 
buildings  have  been  thrown  down  or  otherwise  injured  by 
the  expansion  of  large  iron  rods  (anchors)  built  into  the 
masonry  with  the  design  of  strengthening  them.     The  Bun- 
ker Hill  monument  is  daily  bent  out  of  a  perfect  vertical 
by  the  heat  of  the  sun  expanding  the  granite  of  which  it 
is  built.     The  mechanical  arts  are,  in  fact,  full  of  beautiful 
applications  of  the  principles  of  expansion.     Among  these 
we  may  mention 

107.  The  Compensation  Pendulum,  adapted  to  regulating 
the  rate  of  time-pieces.     The  length  of  the  pendulum  is 

105.  What  is  the  law  of  expansion  in  gases  ?  How  much  does  air  dilate 
for  each  degree  ?  106.  Mention  some  instances  of  expansion  in  the  arts. 


HEAT. 


altered  by  variations  of  temperature,  and  of  course  the  rate 
of  the  clock  is  disturbed.     A  perfect  compensation  for  this 
g       error  is  obtained  by  the  use  of  a  compound 
pendulum  of  brass  and  iron,  or  other  two 
metals,  arranged  as  is  shown  in  fig.  92,  in 
such  a  manner  that  the  expansion  of  one 
metal  downward  will  exactly  counteract  that 
of  the  other  metal  upward;   thus  keeping 
the  ball  of  the  pendulum  at  a  uniform  dis- 
tance from  the  point  of  suspension.     The 
shaded  bars  represent  the  iron,  and  the  light 
ones  the  brass.     The  same  object  is  accom- 
plished by  using  mercury,  as  shown  in  fig. 
91,  contained  in  a  glass  or  steel  vessel  at  the 
end  of  the  pendulum-rod.     The  expansion 
which  lengthens  the  rod  also  increases  the 
volume  of  the  mercury;  this  increase  of  bulk 
in  the  mercury  raises  the  centre  of  gravity  to 
an  exactly  compensating  amount,  and  the 
Fig  91.     Fi    92  c^oc^  remains  unaltered  in  rate.  Watches  and 
'  chronometers  are  regulated  by  a  like  beautiful 
contrivance.    The  balance-wheel,  (fig.  93,)  on  whose  uniform 
motion  the  regularity  of  the  watch  or  chronometer  depends, 
is  liable  to  a  change  of  dimensions  from 
heat  or  cold.     If  made  smaller,  it  will 
move  faster,  and  if  larger,  slower.     To 
avoid  this  error,  the  outside  of  the  wheel 
is  made  of  brass,  the  inside  of  steel,  and 
cut  at  two  opposite  points;  one  end  of 
each  part  is  screwed  to  the  arm,  and  the 
loose  ends  of  the  rim,  being  united  by  a 
Fig.  93.  screw,  are  drawn  in  or  thrown  out  by 

the  changes  of  temperature,  in  precise  proportion  to  the 
amount  of  change ;  thus  perfectly  adapting  the  revolution 
of  the  wheel  to  the  force  of  the  spring.  The  principle  of 
this  wheel,  it  will  be  seen,  is  the  same  as  in  the  compound 
bars,  (107.)  A  pendulum  of  pine-wood  is  sometimes  em- 
ployed for  clocks,  because  it  is  so  little  changed  by  varia- 
tions of  temperature. 

108.  The  unequal  expansion  of  solids  is  well  shown  by 


107.  What  is  the   compensation  pendulum?     What  the  mercurial? 
What  is  the  compensation  balance  ? 


THE   THERMOMETER.  75 

joining  firmly,  by  rivets,  two  bars,  one  of  iron  and  one  of 

brass,  as  in  fig.  94.    When  Fio.  94> 

they  are  heated,  the  brass  / 

expanding  most,  will  cause          ~ 

the  compound  bar  to  bend, 

as  shown  in  the  fig.  95.      ^^~^~^  '   '  '  :^r~~^=~^^^, 

If  they  are  cooled  by  ice,  ^^"^  ""-•^ 

the  brass  contracting  most,  lg'     ' 

will  bend  the  united  metals  in  an  opposite  direction, 

The  Thermometer. 

109.  The  Thermometer  is  an  instrument  for  measuring 
heat  by  the  expansion  of  various  liquids  and  solids.    This  in- 
strument was  invented  by  Sanctorio,  an  Italian,  in  A.  D.  1590. 
His  was  an  air-thermometer,  such  as  is  figured  in  the  context. 
A  bulb  of  glass  with  a  long  stem  is  placed  with  its     ^-^ 
mouth  downward,  in  a  vessel  containing  a  portion 

of  colored  water,  (fig.  96.)  A  part  of  the  air  r 
being  first  expelled  from  the  ball  by  expansion,  the 
fluid  rises  to  a  convenient  point  in  the  stem,  to  which 
is  attached  a  scale  of  equal  parts,  with  degrees  or 
divisions  marked  by  some  arbitrary  rule.  Thus 
arranged,  the  instrument  indicates  with  great  deli- 
cacy any  limited  change  of  temperature  in  the  sur- 
rounding air.  The  portion  of  air  confined  in  the 
ball,  when  heated,  expands,  and  pressing  on  the 
column  of  fluid  in  the  stem,  drives  it  down,  accord- 
ing to  the  amount  of  expansion  or  the  degree  of 
heat;  and  the  reverse  results  from  a  decrease  of 
temperature.  The  air  thermometer  has  given  place  to 

110.  The  Common  Thermometer. — This  instrument  indi- 
cates changes  of  temperature  by  the  expansion  of  mercury  or 
of  alcohol  contained  in  the  bulb  blown  upon  the  end  of  a  very 
fine  glass  tube.  Mercury  possesses  very  remarkable  properties 
fitting  it  for  a  thermometric  fluid :  it  may  easily  be  obtained 
pure ;  its  rate  of  expansion  is  singularly  uniform  between 
its  boiling  and  freezing  points,  and  the  range  of  temperature 
between  these  points  is  greater  than  in  any  other  fluid,  (about 
660°  Fahr.)    For  very  low  temperatures  alcohol  is  preferred, 
as  it  has  never  yet  been  solidified,  even  with  the  intensest 

108.  Describe  figs.  94  and  95.     109.  What  is  the  thermometer?     De- 
ncribe  Sanctorio's  thermometer.   110.  Describe  the  common  thermometer. 


HEAT. 


artificial  cold  of  the  carbonic  acid  bath  (§151,)  or  of  the  arctio 
regions.  The  precautions  needed  to  make  a  thermometer, 
such  as  will  meet  the  demands  of  modern  science,  are  too 
numerous  to  be  fully  described  here.  Suffice  it  to  say,  that 
by  expanding  the  air  in  the  empty  ball,  while  the  open  end 
of  the  tube  is  covered  with  mercury,  a  portion  of  it  is  carried 
in  by  the  pressure  of  the  atmosphere,  and  by  boiling  this, 
all  air  is  expelled  and  the  tube  entirely  filled 
with  mercury.  The  quantity  is  so  adjusted 
by  trial  that  it  will  stand  at  a  convenient 
height  in  the  tube.  Finally,  the  tube  is  sealed 
by  the  lamp,  while  the  contained  mercury  is 
expanded  to  completely  fill  it.  The  empty 
space  in  a  good  thermometer  is  therefore  a 
torricellian  vacuum. 

111.  Graduation  of  Thermometers. — The 
scales  adapted  to  the  thermometer  in  various 
countries  are  divided  into  arbitrary  degrees, 
and,  unfortunately  for  science,  the  scales  differ 
widely.  There  are,  however,  two  fixed  points 
in  all,  which  are  determined  by  direct  ex- 
periment. These  are  the  boiling  and  freezing 
points  of  water,  or,  more  accurately,  the  melt- 
ing point  of  ice.  The  space  between  these 
two  points  is  divided  into  a  certain  number 
of  equal  parts,  according  to  the  scale  to  be 
employed.  In  France,  and  on  the  continent 
of  Europe  generally,  the  scale  of  Celsius,  or 
Centigrade,  is  employed,  which  divides  this 
space  into  100  degrees.  In  England  and 
America  the  scale  of  Fahrenheit,  a  Hollan- 
der, is  adopted.  This  scale  adopts  for  its 
zero  point  the  cold  produced  by  a  freezing 
mixture  of  snow  and  salt;  which  its  author 
assumed  to  be  the  greatest  possible  cold.  The 
word  zero  signifies  nothing,  but  we  know  that 
as  cold  is  the  mere  absence  of  heat,  it  is  hope- 
less to  expect  an  absolute  zero.  The  scale 
of  Reaumur,  adopting  the  melting  of  ice  as 
zero,  divides  the  space  between  that  point  and 
the  boiling  of  water  into  80  degrees.  The 


130- 


100 


90- 1 : 


50-  H 


Fig.  97. 


111.  How  are  thermometers  graduated  ?     What  are  fixed  points  ? 


THE   THERMOMETER.  77 

Bcalc  of  De  Lisle,  which  is  no  longer  used,  read  downward 
from  zero  at  boiling  water  to  150°,  the  freezing  of  the  same. 
Annexed,  in  fig.  97,  we  have  these  four  scales  compared.  It 
will  be  seen  that  zero  Centigrade  is  zero  Reaumur  and  32° 
Fahrenheit;  while  100° ,0-  =  80°  R.  =212°  F.  In  other 
words,  these  three  scales  divide  the  space  between  the  two 
fixed  points  respectively  into  100°  0.,  80°  K,  and  180°  F. ;  or, 
reducing  to  smallest  terms,  5°  C.  =  4°  R,  .=  9°  F.  To  reduce 
Centigrade  to  Fahrenheit,  we  can  multiply  by  9  and  divide 
by  5,  and  add  32°  to  the  quotient,  and  vice  versa.  Suppose 
we  wish  to  know  what  70°  C.  is  on  Fahrenheit's  scale;  we 
have  the  proportion  5  :  9  : :  70° :  126°.  If  we  add  32°,  which 
is  the  difference  between  zero  of  F.  and  C.,  we  have  126°  -f- 
32°  =  158°,  which  is  the  number  required,  for  70°  C.  = 
158°  F.  In  stating  thermometrical  degrees,  the  sign  -f-  is 
used  for  points  above  zero,  and  —  for  those  below.  Fahren- 
heit's scale  is  the  one  employed  in  this  work. 

112.  The  Self-Registering  Thermometer  is  a  form  of  the 
instrument  contrived  for  the  purpose  of  ascertaining  the 
extremes  of  variations  which  may  occur,  as,  for  instance, 
during  the  night.  It  consists  of  two  horizontal  thermometers 
attached  to  one  frame,  as  in  fig.  98 ;  b  is  a  mercurial  ther- 


Fig.  98. 

mometer,  and  measures  the  maximum  temperature,  by  push- 
ing forward,  with  the  expansion  of  the  column,  a  short  piece 
of  steel  wire,  of  such  size  as  to  move  easily  in  the  bore  of 
the  tube ;  it  is  left  by  the  mercury  at  the  remotest  point 
reached  by  the  expansion ;  a  is  a  spirit-of-wine  thermometer, 
and  measures  the  minimum  temperature.  It  contains  a  short 
cylinder  of  porcelain,  shown  in  the  figure,  which  retires  with 
the  alcohol  on  the  contraction  of  the  column  of  fluid,  but 
does  not  advance  on  its  expansion. 

Name  the  three  scales.  What  is  boiling  water  in  each  ?  What  freez- 
ing? Convert  Centigrade  70°  to  Fahrenheit.  112.  What  is  the  self- 
registering  thermometer  ? 


78 


HEAT. 


o 


Fig.  99. 


113.  The  Differential  Thermometer  is  a  form  of  air-ther- 
mometer, so  named  because  it  denotes  only  differences  of 

temperature.  It  consists  of  two  bulbs 
on  one  tube,  bent  twice  at  right  angles^ 
and  supported,  as  shown  in  fig.  99.  A 
little  sulphuric  acid,  water,  or  other 
fluid  partly  fills  the  stem  only.  When 
the  bulbs  of  this  instrument  are  heated 
or  cooled  alike,  no  change  is  seen  in  the 
position  of  the  column ;  but  the  instant 
any  inequality  of  temperature  exists 
between  them,  as  from  the  bringing  the 
hand  near  one  of  them,  the  column  of 
fluid  moves  rapidly  over  the  scale.  A 
modification  of  this  instrument,  of  great  delicacy,  was  con- 
trived by  Dr.  Howard  of  Baltimore,  in  which  sulphuric  ether 
was  the  fluid  used,  the  bulbs  being  vacuous  of  air. 

114.  A  Pyrometer  is  an  instrument  for  measuring  liiyh 
temperatures.     As  mercury  boils  at  about  660°,  we  can 
estimate  the  temperature  of  fused  metals,  and  the  like,  only 
by  the  expansion  of  solids.     The  only  instrument  of  this 
sort  which  we  need  mention,  as  it  is  the  only  one  susceptible 
of  accuracy,  is  Daniell's  Register  Pyrometer.    It  consists  of 
a  hollow  case  of  black-lead,  or  plumbago,  into  which  is 
dropped  a  bar  of  platinum,  secured  to  its  place  by  a  strap 
of  platinum  and  a  wedge  of  porcelain.     The  whole  is  then 
heated,  as,  for  instance,  by  placing  it  in  a  pot  of  molten  silver, 

whose  temperature  we  wish  to 
ascertain.  The  metal  bar  expands 
much  more  than  the  case  of  black- 
lead,  and  being  confined  from 
moving  in  any  but  an  upward 
direction,  drives  forward  the  arm 
of  a  lever,  as  shown  in  fig.  100, 
over  a  graduated  arc,  on  which 
we  read  the  degrees  of  Fahren- 
heit's scale  :  (this  graduation  has 
been  determined  beforehand  with 
great  care.)  This  instrument 
gives  very  accurate  results;  by 
Fig.  100.  it  the  melting  point  of  cast  iron 


113.  What  the  differential?     114.  What  are  pyrometers?     Describe 
Daniell's. 


SPECIFIC   HEAT.  79 

has  been  found  to  be  2786°  F.,  and  of  silver  I8600  F. 
The  highest  heat  of  a  good  wind-furnace  is  probably  not 
much  above  3300°.  Fig.  88  (101)  is  a  pyrometer  of  ordi- 
nary construction. 

115.  Breguet's  thermometer  is  constructed 
upon  the  principle  of  the  unequal  expansion 
of  metals,  (107.)    A  compound  piece  of  me- 
tal is  formed  by  soldering  together  two  equal 
masses   of  silver  and   platina — two    metals 
whose  expansion  is  very  unequal.     This  is 
rolled  thin  and  coiled  into  a  spiral  as  shown 
in  a  b,  (fig.  101.)     It  is  suspended  from  a 

fixed  point  p,  while  its  lower  end  is  free  and  carries  an 
index  i.  Variations  of  temperature  cause  this  spiral  to  un- 
wind or  wind  up,  and  these  motions  are  indicated  by  the 
motion  of  the  pointer.  This  is  a  more  delicate  thermometer 
than  any  mercurial  or  spirit  one.  A  beautiful  modification 
of  Breguet's  thermometer  has  been  contrived  by  Mr.  Saxton, 
to  measure  the  temperature  of  the  sea  in  deep  soundings. 

116.  All  thermometers  for  accurate  research  are  divided 
on  the  glass  stem  by  aid  of  a  graduating  engine  and  mi- 
crometer }  each  instrument  being,  according  to  the  plan  of 
Regnault,  graduated  by  an  arbitrary  scale. 

Capacity  for  Heat,  or  Specific  Heat. 

117.  Different  bodies  have  different  capacities  for  heat. 
If  equal  measures  of  mercury  and  of  water,  for  example, 
are  exposed  to  the  same  source  of  heat,  the  mercury  will 
reach  a  given  temperature  more  than  twice  as  soon  as  the 
water,  and  it  will  cool  again  in  half  the  time.     Mercury  is 
said,  therefore,  to  have  only  half  the  capacity  for  heat  which 
water  has.     We  learn  by  trial  that  each  substance  in  like 
manner  has  its  own  relations  to  heat  as  respects  capacity. 
This  is  called  also  specific  heat,  a  term  synonymous  with 
capacity.     Water  is  adopted  as  the  standard  of  comparison 
for  this  property,  and  the  trial  is  usually  made  upon  equal 
weights  rather  than  upon  equal  measures  of  the  substances 
compared.     Specific  heat  connects  itself  curiously  with  the 
atomic  constitution  of  matter.     Several  modes  may  be  em- 

115.  What  is  the  metallic  thermometer?  116.  How  are  thermometers 
accurately  graduated  ?  117.  What  is  capacity  for  heat  ?  Give  examples. 
What  is  specific  heat? 


80  HEAT. 

ployed  to  determine  it;  as  by  mixture,  by  melting,  by 
warming,  or  by  cooling.  The  determination  of  this  property 
is  called  calorimetry,  and  the  modes  of  experiment  most 
usual  are  either  by  mixture  or  by  the  fusion  of  ice. 

118.  The  Method  of  Mixtures. — If  a  pint    measure    of 
water,  at  150°,  be  mixed  quickly  with  an  equal  measure  of 
the  same  fluid  at  50°,  the  two  measures  of  fluid  will  have 
the  temperature  of  100°,  or  the  arithmetical  mean  of  the 
two  temperatures  before  mixture.     If,  however,  we  rapidly 
mingle  a  measure  of  water  at  150°,  and  an  equal  measure 
of  mercury  at  50,  we  shall  find  that  they  will  have  the  tem- 
perature of  118°.     The  mercury  has  gained  68°,  and  the 
water  lost  about  half  as  much,  or  only  32°.     Hence  we 
infer  that  the  same  quantity  of  heat  can  raise  the  tempera- 
ture of  mercury  through  twice  as  many  degrees  as  that  of 
water,  and  that  the  specific  heat  of  water  will  be  to  that 
of  mercury  as  1 :  047,  when  compared  by  measure.     But 
if  we  divide  this  number  (0-47)  by  the  density  of  mercury 
(13-5)  we  obtain  the  number  0.035,  which  expresses  the 
specific  heat  by  a  comparison  of  weights.     Water  has  then 
more  than  30  times  the  capacity  for  heat  which  is  found  in 
mercury ;  and  in  this  peculiarity  we  find  an  important  rea- 
son of  the  singular  fitness  of  this  fluid  metal  for  the  con- 
struction of  thermometers. 

119.  El/  the  melting  of  ice  in  the  calorimeter  of  Lavoisier, 
is  in  fig.  102,  the  capacity  of  most  substances  for  heat  has 
»een  determined.      A  set  of  metallic  vessels  abc  are  so 

arranged  that  when  a  warm  body  is 
placed  in  c,  all  the  heat  it  gives  off  in 
cooling  will  go  to  melt  the  lumps?  of  ice 
surrounding  it.  The  water  of  fusion 
escapes  at  the  cock  s,  and  is  measured 
in  the  graduated  glass  beneath.  To 
cut  off  the  heat  of  the  surrounding  air, 
the  space  between  a  and  b  is  also  filled 
with  ice.  The  water  which  melts  from 
this  portion  is  carried  away  by  r.  In 
this  apparatus  the  relative  capacities 
.  102  of  all  solid  and  fluid  substances  may, 

with  proper  precautions,  be  accurately 


What  is  calorimetry  ?     118.  Describe  the  method  of  mixtures.     119. 
What  is  Lavoisier's  calorimeter  ? 


CHANGES   PRODUCED   BY   HEAT. 


81 


determined  by  the  respective  measures  of  water  which  flow 
from  s  during  the  experiment,  in  which  each  body  cools 
from  an  agreed  temperature,  (e.  g.  212°)  to  32  °,  the  constant 
temperature  of  c.  The  same  result  may  be  reached  in  some 
cases  more  simply  by  employing  a  large  lump 
of  solid  ice  a  (fig.  103)  in  which  a  well  W  has  jj 
been  scooped  out,  and  covered  by  a  lid  of  ice  b. 
Any  solid  substance,  or  a  fluid  contained  in  a 


glass  flask,  may  be  placed  in  W,  and,  when  the  | 

temperature  has  fallen  to  32°,  the  water  con- 

tained  in  W  may  be  measured  as  before.     To  es- 

timate the  capacity  of  heat  in  gases,  atmospheric    air   is 

chosen  as  unity  —  and  the  method  of  melting  is  adopted  by 

passing  a  certain  volume  of  gas  through  a  tube  refrigerated 

by  ice. 

120.  It  is  plain,  from  what  has  been  said,  that  the  capa- 
city of  bodies  for  heat  is  a  phenomenon  not  indicated  by 
the  thermometer.  In  the  foregoing  experiments,  water  and 
mercury  have  been  each  heated  to  212°,  and  yet  the  result 
demonstrates  that  an  equal  weight  of  water  contains  at  that 
temperature  about  30  times  as  much  heat  as  the  mercury. 
The  thermometer  can  indicate  only  actual  intensity  of  heat, 
and  not  its  volume  or  quantity. 

In  the  following  table  of  specific  heats,  it  will  be  seen 
that  this  property  has  much  connection  with  the  physical 
condition  of  bodies  as  respects  fluidity  or  crystalline  ar- 
rangements, as  is  evident  by  comparing  the  capacity  of 
water  and  ice,  and  of  the  various  forms  of  carbon  :  — 


Water 1000 

Ice 513 

Turpentine 468 

Carbon  (charcoal)  241 

Anthracite  (Pa.)  201 

Graphite 201 

Diamond 146 

Steel 116 


Sulphur 177 

Sulphur       lately 

fused 184 

Ether 520 

Alcohol 660 

Mercury 33 


Iron. 

Copper 


114 


Zinc 95 

Brass 94 

Silver 57 

Antimony 51 

Gold 32 

Lead 31 

Phosphorus 118 


95  !  Glass 197 


Changes  produced  Tjy  Heat  in  the,  State  of  Bodies. 

121.  Fluidity  \s  a  result  of  temperature,  as  is  seen  in  the 
familiar  case  of  water,  which  is  either  ice,  water,  or  steam, 


What  simpler  one  is  described  ?     120.  What  does  the  thermometer  lail 
in  indicating?     Give  examples  from  table.     121.  What  is  fluidity  ? 

6 


82  HEAT. 

according  to  the  temperature  to  which  it  is  subjected.  Many 
solids  can  be  melted  by  an  increase  of  temperature,  and  the 
melting  point  is  always  the  same  for  a  given  solid.  Some 
substances  pass  at  once  to  the  fluid  state,  while  others, 
as  wax,  assume  an  intermediate  pasty  condition,  and  others, 
like  ice,  fuse  very  slowly  indeed.  The  degree  of  heat  at 
which  bodies  melt  varies  exceedingly.  Thus  platinum  is 
not  melted  at  3280°.  Iron  melts  at  about  2800° ;  gold,  at 
2016°;  silver,  1873°;  zinc,  773°;  lead,  612°;  tin,  442°; 
Newton's  alloy,  212°;  potassium,  136°  ;  phosphorus,  108°; 
wax,  142°;  tallow,  92°;  olive  oil,  36°;  ice,  32°;  milk, 
30°;  wines,  20°;  mercury, —39°;  fluid  ammonia, —46°; 
ether,  — 47°;  while  pure  alcohol  is  not  solid  at  175°  below 
Fahrenheit's  zero. 

122.  Liquefaction  is  attended  by  a  remarkable  absorption 
of  heat.  We  have  already  seen  that  two  equal  measures  of 
water  at  different  temperatures  assume  when  mingled  the 
mean  of  their  previous  temperatures,  (118.)  If,  however, 
we  take  a  pound  of  ice  at  32°,  and  a  pound  of  water  at 
212°,  we  shall  find,  when  the  ice  is  melted,  that  the  two 
pounds  of  water  have  the  temperature  of  only  52°  ;  the  ice 
gains  only  20°,  while  the  water  has  lost  160°.  There  are, 
then,  140°  of  heat  lost  in  producing  this  change.  We  can 
take  another  mode  of  trial.  Let  us  expose  a  pound  of  ice 
and  a  pound  of  water,  each  at  32°,  to  a  constant  source  of 
heat,  in  two  vessels  every  way  alike,  and  note  the  changes 
of  temperature  by  the  thermometer.  The  same  quantity 
of  heat  is  flowing  into  each  vessel.  When  the  ice  is  all 
melted,  we  shall  find  that  the  water  into  which  it  is  con- 
verted has  still  only  the  temperature  of  32°,  while  the  other 
pound  of  water  has  risen  from  32°  to  172°  :  here  again  we 
see  the  loss  of  140°  of  heat  used  in  converting  the  ice  into 
water.  We  may  reverse  the  last  experiment,  and  take  equal 
weights  of  ice  at  32°  and  water  at  172°  and  mix  them : 
when  the  ice  is  all  melted  the  mixture  will  still  have  the 
temperature  of  only  32° ;  so  that,  in  whatever  way  we  may 
make  the  trial,  we  constantly  observe  the  loss  of  140°  of 
heat.  This  is  called  the  heat  of  fluidity,  it  being  necessary 
to  the  existence  of  the  water  in  a  fluid  state  ]  and  it  is  also 
designated  latent  heat,  because  it  is  lost,  absorbed,  or  con- 
Name  the  fluidity-points  of  several  bodies.  122.  What  phenomenon 
attends  liquefaction?  Give  an  example.  How  is  this  reversed  ?  What 
is  latent  heat? 


CHANGES   PRODUCED    BY   HEAT.  83 

cealed,  as  it  were,  and  no  indication  of  it  can  be  found  by 
the  thermometer. 

123.  This  law  is  equally  illustrated  by  the  slow  freezing 
of  water.  If  a  vessel  filled  with  water  at  52°  be  placed  in 
an  atmosphere  of  32°,  it  will  rapidly  cool  down  to  32°  by 
the  loss  of  20°  of  temperature.  After  this,  it  will,  as  may 
be  seen  by  the  thermometer,  remain  at  32°,  until  it  is  all 
converted  to  solid  ice ;  although  we  cannot  doubt  that  it  is 
all  the  while  giving  out  a  quantity  of  heat,  which  had  before 
been  insensible  or  latent.  If  the  water  had  been  ten 
minutes  in  cooling  from  52°  to  32°,  (or  in  losing  20°,) 
then  it  would  require  one  hour  and  ten  minutes,  or  seven 
times  as  long,  for  it  to  become  completely  frozen.  If,  then, 
in  equal  times  it  lost  equal  degrees  of  heat,  its  latent  heat 
will  be  20°  X  7  =  140°,  which  is  the  same  result  as 
before. 

Thus  we  arrive  at  the  seeming  paradox  that  freezing  is  a 
warming  process.  By  experiment  we  may  show  that  water 
may  be  cooled  some  8  or  9  degrees  below  its  freezing  point 
and  still  remain  liquid,  if  its  surface  be  covered  with  a  thin 
film  of  oil,  or  if  it  is  a  thin  smooth  vessel,  kept  quite  still; 
but  the  least  disturbance  will  cause  it,  when  in  this  situa- 
tion, to  become  solid  at  once,  and  the  temperature  will  im- 
mediately rise  from  23°  or  24°  to  32°.  The  freezing  of  a 
part  has  therefore  given  out  heat  enough  to  raise  the  tem- 
perature of  the  whole  from  24°  to  32°,  or  through  8°.  Our 
domestic  experience  in  cold  climates  often  supplies  examples 
of  this  fact.  The  solidification  of  a  saturated  solution  of  sul- 
phate of  soda  is  also  an  example  of  the  same  nature ;  the  ves- 
sel containing  the  solution  becomes  sensibly  warm.  In  like 
manner,  it  is  true  that  melting  is  a  cooling  process.  A  solid 
can  melt  only  by  absorbing  heat  from  surrounding  bodies, 
which  must,  of  course,  become  cooler.  Hence,  in  part,  the 
cooling  influence  of  an  iceberg,  which  is  often  felt  for  many 
leagues,  or  of  a  large  body  of  snow  on  a  distant  mountain ; 
and  the  chill  felt  in  the  air  on  a  bright  day  in  spring,  when 
snow  is  rapidly  melting  on  the  ground. 

It  is  a  wise  order  of  nature  that  makes  the  freezing  and 
thawing  of  snow  and  ice  extremely  slow  and  gradual  pro- 


123.  Illustrate  it  by  the  freezing  of  water.  How  may  water  remain 
liquid  below  32°?  How  is  freezing  a  warming  process?  What  proof 
of  design  is  here  indicated  ? 


84  HEAT. 

cesses.  If  water  became  solid  at  once  on  reaching  32°,  it 
would  be  suddenly  frozen  to  a  great  depth ;  and  if  ico 
melted  as  quickly  on  reaching  the  same  temperature,  the 
most  sudden  and  dreadful  floods  would  accompany  these 
events,  and  the  common  changes  of  the  seasons  would  bo 
calamitous  to  human  comfort  and  life. 

124.  Freezing  mixtures  owe  their  powers,  to  the  principles 
just  explained.     Ice-cream  is  frozen  by  a  mixture  of  snow 
or  pounded  ice  with  common  salt.     In  this  case,  the  two 
solids  are  rapidly  changed  to  fluids ;  the  ice  is  melted  by 
the  salt,  and  the  salt  is  dissolved  by  the  water  from  the 
melting  ice.     Both  these  operations  absorb  a  large  quantity 
of  heat.   The  surrounding  bodies  are  called  on  to  supply  the 
heat  required,  and  the  cream  in  a  thin  metallic  vessel  cools 
so  rapidly  as  to  be  soon  turned  to  ice.     The  thermometer 
will  fall  in  this  operation  to  0°  F. ;  and  this  was  the  very 
experiment  by  which  Fahrenheit  (111)  assumed  that  he  had 
attained  to  a  true  zen..  of  cold. 

Nitrate  of  ammonia  dissolved  in  water  at  46°  will  sink  the 
temperature  to  zer">,  ami  the  exterior  of  the  vessel  becomes 
at  once  thickly  covered  with  hoar-frost.  Common  saltpetre, 
(nitrate  of  potassa,)  dissolved  in  water,  lowers  its  tempera- 
ture about  15°  or  18°,  and  is  therefore  much  used  in  the  hot 
regions  of  Asia,  where  it  abounds,  for  cooling  wine.  Mer- 
cury may  be  frozen  by  using  a  mixture  of  three  parts  of 
chlorid  of  calcium  and  two  of  dry  snow ;  this  mixture  will 
sink  the  temperature  from  -{-32°  to  — 50°.  Five  parts  of 
finely-powdered  sal  ammoniac  and  five  of  nitre,  dissolved  in 
nineteen  of  water,  will  reduce  the  temperature  from  50°  to 
10°  j  and  a  little  powdered  sulphate  of  soda,  drenched  with 
strong  hydrochloric  acid,  will  sink  the  thermometer  from  50° 
to  0°.  But  the  most  intense  cold  is  that  which  results 
from  the  volatilization  of  liquefied  carbonic  acid  and  nitrous 
oxyd  gases,  by  which  the  enormously  low  temperatures  of 
—175°  and  even  220°  are  reached. 

125.  Diminution  of  volume  causes  a  portion   of  latent 
heat  to  become  sensible.     Air  suddenly  compressed  into  a 
email  space,  as  in  the  fire-syringe,  (fig.  104,)  evolves  heat 
enough  to  fire  a  portion  of  dry  punk  on  the  end  of  the 
piston.     Metals  rapidly  struck,  as  on  an  anvil,  become  hot 


124.  What  are  freezing  mixtures  ?     Give  their  theory.     What  is  the 
most  intense  artificial  cold  ?    125.  What  ignites  tinder  in  the  fire-syringe  ? 


VAPORIZATION.  85 

enough  to  enable  the  smith  to  light  his  fire.  "Wa- 
ter poured  on  quicklime  combines  with  it,  with  the 
evolution  of  much  heat;  the  water  in  this  case 
taking  on  the  solid  form.  Sulphuric  acid  and 
water,  when  mingled,  give  out  great  heat,  and  the 
bulk  of  the  mixture  is  less  than  that  of  the  two 
before  mixing.  Liquefaction  is  always  a  cooling 
process,  and  solidification  or  condensation  a  heat- 
ing one.  A  certain  quantity  of  heat  may  be  con-  Fig.  104. 
sidered  as  necessary  to  preserve  each  body  in  its 
natural  condition :  if  it  be  condensed,  less  is  required,  and 
it  gives  out  the  excess ;  and  if  expanded,  it  absorbs  more. 

Vaporization. —  The  Boiling  Points  of  Bodies. 

126.  A  continuance  of  the  heat  which  melted  the  ice  into 
water,  will  turn  the  water  into  vapor  or  steam.  The  phe- 
nomena which  attend  this  physical  change  are  not  less  curious 
or  instructive  than  the  last. 

If  we  place  a  known  quantity  of  water  over  a  steady  source 
of  heat,  we  shall  see  the  thermometer  indicating  each  mo- 
ment a  higher  temperature,  until,  at  212°,  the  fluid  boils; 
after  which  the  thermometer  indicates  no  further  change, 
but  remains  steady  at  the  same  point  until  all  the  water  is 
boiled  away.  Let  us  suppose  that,  at  the  commencement  of 
the  experiment,  the  temperature  of  the  water  was  62°,  and 
that  it  boiled  in  six  minutes  after  it  was  first  exposed  to  the 
heat :  then  the  quantity  of  heat  which  entered  into  it  each 
minute  was  25°,  because  212°,  the  boiling  point,  less  62°, 
leaves  150°  of  heat  accumulated  in  six  minutes,  or  25°  each 
minute.  Now  if  the  source  of  heat  continue  uniform,  we 
shall  find  that  in  forty  minutes  all  the  water  will  be  boiled 
away;  and  hence  there  must  have  passed  into  the  water,  to 
convert  it  into  steam,  25°  X  40  —  1000°.  One  thousand 
degrees  of  heat,  therefore,  have  been  absorbed  in  the  process, 
and  this  constitutes  the  latent  heat  of  steam.  So  much  heat, 
indeed,  was  imparted  to  the  water,  that  if  it  had  been  a  fixed 
solid,  it  would  have  been  heated  to  redness;  and  yet  the 
steam  from  it,  and  the  fluid  itself,  had  during  the  whole  time 
a  temperature  of  only  212°. 

125.  Give  examples  of  heat  evolved  from  condensation.  126.  What  is 
vaporization  ?  What  is  the  latent  heat  of  water  ?  How  is  it  observed  ? 


86  HEAT. 

127.  The  capacity  of  water  for  heat  is  greater  than  that 
of  any  other  body  known;  and  in  vapor  it  preserves  the 
same  distinction.     The  latent  heat  of  steam  has  been  vari- 
ously stated  by  different  experimenters  at  940°,  956°,  960°, 
$72°,  and  1000°.    The  latest,  and  probably  the  most  accurate 
determination,  is  that  of  Brix,  viz.  972°.    The  latent  heat  of 
vapors  has  no  relation  to  their  points  of  boiling.     The  supe- 
riority of  vapor  of  water  in  respect  to  latent  heat  will  be  seen 
by  a  comparison  with  that  of  several  other  bodies,  viz.  latent 
heat  of  vapor  of  water  =972°,  of  ammonia  837°,  of  alcohol 
386°,  of  ether  162°,  of  oil  turpentine  133°.    The  large  amount 
of  latent  heat  contained  in  steam  becomes  again  sensible  on 
its  condensation  to  water;  thus  enabling  us  to  make  great 
use  of  it  as  a  means  of  conveying  heat.     The  steam,  so  to 
speak,  takes  up  a  large  quantity  of  heat,  and  transports  it 
to  the  point  where  we  wish  it  applied.     One  gallon  of  water 
converted  into  steam,  at  the  ordinary  pressure  of  the  atmo- 
sphere, will  raise  five  gallons  and  a  half  of  ice-cold  water 
to  the  boiling  point.     In  this  way  we  can  boil  water  in 
wooden  tanks,  heat  large  buildings  by  steam-pipes,  and  make 
numberless  other  useful  applications  of  steam-heat  in  the  arts. 
It  is  found  in  practice  that  to  heat  buildings  by  steam,  every 
2000  feet  of  space  to  be  heated  to  75°  requires  one  cubic 
foot  of  boiler  capacity,  and  that  every  square  foot  of  radiat- 
ing surface  on  the  conducting  pipes  will  heat  200  cubic  feet 
of  space. 

128.  The  boiling  point  of  each  fluid  is  constant,  other 
things  being  equal,  but  is  peculiar  to  itself;  thus,  ether  boils 
at  96°,  ammonia  at  140°,  alcohol  at  173°,  water  at  212°, 
nitric  acid  250°,  oil  turpentine  314°,  phosphorus  554°,  sul- 
phuric acid  620°,  whale-oil  630°,  and  mercury  at  662°. 

129.  Boiling  is  the  mechanical  agitation  of  a  fluid  by  its 
own  vapor.     This  happens  whenever  the  liquid  becomes  so 
hot  that  its  vapor  can  rise  in  bubbles  to  the  surface,  uncou- 
denscd  by  atmospheric  pressure  or  by  the  temperature  of 
the  fluid. '   The  elasticity  or  tension  of  the  vapor  then  be- 
comes greater  than  the  united  pressure  of  the  fluid  and  the 
air.    When  the  boiling  is  vigorous,  a  great  number  of  these 
bubbles  of  uncondensed  vapor  rise  to  the  surface  at  the  same 


127.  What  capacity  has  water  for  heat  ?  Give  other  latent  heats.  Why 
+he  superiority  of  water  for  steam  piy-poses  ?  128.  What  of  the  boiling 
points  of  fluids?  129.  What  is  boiling? 


VAPORIZATION. 


87 


instant,  and  the  liquid  is  thrown  into  violent  agitation.  If 
a  vessel  containing  cold  water  be  heated  suddenly,  the  lowei 
surface  receives  the  most  heat ;  bubbles  of  vapor  are  formed, 
and  rise  a  little  way,  when,  meeting  the  colder  water,  the 
vapor  is  at  once  condensed,  and  the  liquid,  before  sustained 
by  the  elastic  vapor,  falls  with  a  blow  on  the  bottom  of  the 
vessel,  often  destroying  it,  if  of  glass. 

130.  The  boiling  point  is  much  affected  by  the  nature 
and  condition  of  the  vessel.    In  a  metallic  vessel,  water  boils 
at  210°  and  211°.  If  a  glass  vessel  be  coated  inside  with  shel- 
lac, water  boils  in  it  at  211°;  but  if  it  be  thoroughly  cleaned 
with  sulphuric  acid,  water  in  it  may  be  heated  to  221°  or  more, 
without  the  escape  of  bubbles.     A  few  grains  of  sand,  a  little 
fragment  of  wire,  or  a  small  piece  of  charcoal  will,  however, 
at  once  equalize  these  differences,  and  cause  the  water  to 
boil  steadily  at  212°.     This  simple  means  will  prevent  the 
unpleasant  jar  from  sudden  escape  of  vapor,  and  frequent 
fracture  of  the  glass  vessel.     The  boiling  point  is  more  re- 
markably affected  by  variations  in  atmospheric  pressure  than 
by  any  other  cause,  and  we  shall  presently  advert  more  in 
detail  to  the  phenomena  connected  with  it. 

131.  Spheroidal  State  of  Liquids. — If  drops  of  water  are 
let  fall  on  a  metallic   plate  heated  considerably  above  the 
boiling  point,  it  is  observed  that  they  do  not 
evaporate  very  rapidly,  and  that  there  is  no  hiss- 
ing sound,    while  the   globules  of  water   roll 

about  quietly,  floating,  as  it  were,  over  the  hot 
surface.  Thus  situated,  water  is  said  to  be  in 
the  "  spheroidal  state,"  a  term  employed  by  M. 
Boutigny,  who  has  made  many  curious  and  in- 
structive experiments  on  this  subject.  Water 
passes  into  this  condition  at  340°,  and  may  at- 
tain it  even  at  288°.  A  grain  and  a  half  of  water 
in  this  state  at  392°  requires  3-30  minutes  to 
evaporate;  at  a  dull  red-heat,  the  same  quantity 
will  last  1-13  minutes,  and  at  a  bright  red,  0-50, 
the  rate  of  evaporation  increasing  with  the  tem- 
perature. The  water,  in  these  experiments, 
does  not  touch  or  wet  the  hot  surface,  but  is 
kept  at  a  sensible  distance  from  it  by  the  elas-  FiS- 105- 


130.  What  affects  the  boiling  point?     131.  What  is  the  spheroidal 
state  ?     Describe  the  experiment  in  fig.  105. 


88 


HEAT. 


106 


tic  force  of  an  atmosphere  of  its  own  vapor,  as  well  also  as 
by  the  repulsive  action  of  hot  surfaces.  The  vapor  is  a 
non-conductor,  and  its  formation  abstracts  the  sensible  heat 
from  the  fluid  ;  so  that,  notwithstanding  the  proximity  of 
the  red-hot  metal,  the  temperature  of  the  fluid  is  found  to  be 
always  lower  than  its  boiling  point,  being,  for  water,  2050<7; 
for  alcohol,  168°  ;  for  ether,  93°-6  ;  for  hydrochloric  ether, 
500<9,  and  for  sulphurous  acid  13°-1.  The  temperature  is 
estimated  as  shown  in  fig.  105,  where  the  liquid  is  contained 
in  a  metallic  capsule  in  the  flame  of  a  good  eolipile. 

182.  If  a  thick  and  heavy  silver  capsule  is  heated  to  full 
whiteness  over  the  eolipile,   it  may  by  an 
adroit  movement  be  filled  entirely  with  wa- 
ter, and   set   upon   a  stand,  some   seconds 
before  the  heat  declines  to  the  point  when 
contact  can  occur  between  the  liquid  and  the 
metal.    When  this  happens,  the  water,  be- 
fore quiet,  bursts   into  steam  with  almost 
explosive  violence,  and  is  projected  in    all 
directions,  as  shown  in  fig.  106. 
On  the  principle  explained,  the  hand  may  be  bathed  in  a 
vase  of  molten  iron,  or  passed  through  a  stream  of  melted 
metal  unharmed  ;  and  we  find  here  an  explanation  of  the 
success  of  some  instances  of  magic. 

133.  The  pressure  of  the  atmosphere  determines  the  boiling 
point  of  fluids.  It  follows,  therefore,  that  by  a  di- 
minution of  pressure,  water  may  be  made  to  boil 
at  a  much  lower  temperature  than  212°.  If  we 
place  some  warm  water  in  a  glass  under  the  air- 
pump  bell  (fig.  107)  and  exhaust  the  air,  the  water 
will  boil  vigorously,  although  the  temperature,  as 
noted  by  tne  thermometer,  is  observed  to  fall  con- 
stantly. So,  in  ascending  high  mountains,  the 
boiling  point  falls  with  the  elevation,  from  the  diminished 
pressure  of  the  air.  On  this  account,  a  difficulty  is  expe- 
rienced at  the  hospice  of  Saint  Bernard,  on  the  Swiss  Alps, 
in  cooking  eggs  and  other  viands  in  boiling  water.  This 
place  is  8400  feet  above  the  sea,  and  water  boils  there  at 
196°  :  on  the  summit  of  Mount  Blanc,  it  boils  at  184°.  We 


107 


132.   Describe  fig.  106.     Why  can  the  hand  be  safely  plunged  in  fluid 
•on?    13.3.  What  determines  the  boiling  point  of  fluids  ?    How  is  it  OB 


iron  ? 


mountains  ? 


VAPORIZATION. 


89 


learn  that  it  is  the  temperature,  and  not  the  boiling  which 
performs  the  cooking.  The  Rev.  Dr.  Wollaston  proposed  to 
determine  the  height  of  mountains  by  the  boiling  point.  He 
found  an  ascent  of  530  feet  to  be  equal  to  a  decrease  of  1° 
in  the  boiling  point ;  and  with  a  thermometer  having  large 
spaces  considerable  accuracy  may  be  attained.  In  deep  pita 
(as  in  mines)  the  boiling  point  rises. 

134.  The  culinary  paradox  gives  a  very  good  illustration 
of  the  phenomena  of  boiling  under  diminished  pressure.  A 
small  quantity  of  water  is  boiled  in  a  glass  vessel,  as  in  the 
figure :  when  the  water  is  actively  boiling,  a  good  cork  is 
firmly  inserted,  and  the  vessel  removed  from  the  heat.  It 
may  now  be  supported  in  an  inverted  position,  with  the 
mouth  under  water,  as  seen  in  the  figure.  The  boiling  will 
still  continue,  even  more  rapidly  than  before ;  and  if  we  at- 
tempt to  check  it  by  affusion  of  cold  water,  we  shall  only 
cause  it  to  boil  more  vehemently.  A  little  hot  water  will, 
however,  at  once  arrest  the  ebullition.  In  this  case,  the  air 
is  driven  out  of  the  vessel  on  the  first  boiling  of  the  water; 
and,  as  we  close  the  orifice  while  the  steam  is  still  issuing, 
there  is  only  the  vapor  of  water  in  the  cavity. 
As  this  condenses  from  cooling,  the  pressure 
on  the  water  diminishes,  and  it  boils  more 
easily  from  the  heat  it  still  contains:  the  affu- 
sion of  cold  water,  by  producing  a  more  per- 
fect condensation,  occasions  a  more  violent 
ebullition.  Hot  water,  however,  increases  the 
elasticity  of  the  uncondensed  vapor,  and  re- 
presses the  boiling.  These  alternations  can 
be  produced  as  long  as  the  water  in  the  vessel 
is  warmer  than  the  cold  water  poured  on  it. 
When  cold,  the  space. over  the  water  will  be  a 
good  vacuum,  and  if  we  turn  the  water  from 
the  ball  into  the  neck,  it  will  fall  like  a  solid 
body,  with  a  smart  blow  and  rattling  sound. 
This  is  sometimes  called  the  water -hammer. 
The  perfection  of  the  vacuum  can  be  tested 
by  withdrawing  the  cork  under  water :  the 
pressure  of  the  atmosphere  will  then  drive  in 


Fig.  108. 


a  quantity  of  water  equal  to  the  vacuum  produced  by  the 
first  expulsion  of  the  air. 


134.  What  is  the  culinary  paradox  ?     Explain  the  continued  boiling. 


90  HEAT. 

135.    The  Pulse    Glass  of   Dr. 
Franklin  is  a  very  good  illustration, 
F.  also,  of  boiling  under  diminished 

pressure ;  and  the  cool  sensation  felt 

by  the  hand  at  the  instant  when  the  fluid  boils  most  violently, 
is  proof  of  the  heat  absorbed  in  converting  a  part  of  the 
fluid  into  vapor. 

Practical  application  of  these  facts  is  made  in  the  arts  on 
a  large  scale,  as  in  manufacturing  sugar.  The  boiling  of 
the  syrup  is  performed  in  vacuo,  in  large  pans  of  copper, 
holding  several  hundred  gallons,  the  air  and  vapor  being 
removed  from  the  vessels  by  the  air  pump  of  a  steam-engine  : 
the  syrup  is  thus  rapidly  boiled  down  at  a  temperature  of 
150°  to  180°,  without  any  danger  of  burning.  Vegetable 
extracts  are  frequently  made,  and  saline  solutions  boiled,  in 
the  same  way.  Nothing  in  the  arts  shows  more  clearly  the 
value  and  beauty  of  scientific  principles. 

136.  Elevation  of  the  Boiling  Point  by  Pressure. — In 
Papin's  digester,  (fig.  110,)  a  strong  iron  vessel  with  a  safety- 
valve,  water  may  be  heated  under  the  pres- 
sure of  its  own  vapor  to  400°,  or  higher. 
This  apparatus  may  be  so  arranged  with  a 
thermometer  and  pressure  gauge,  (fig.  Ill,) 
that  we  can  note  the  relations  of  pressure  and 
temperature  (Marcet's  apparatus) :  the  ther- 
mometer-ball is  in  the  steam  cavity;  the 
gauge  descends  into  some  mercury  in  the 
bottom.  It  is  supported  by  a  tripod /over 
a  lamp  e,  and  a  stopcock  d  cuts  off  the  ex- 
Fig.  110.  ternal  air,  when  the  boiling  has  commenced. 
As  the  steam  accumulates,  it,  pressing  on  the  mercury,  forces 
it  up  the  tube,  against  the  imprisoned  air  in  the  gauge  I. 
When  the  gauge  shows  double  the  pressure  of  the  air,  the 
thermometer  will  indicate  a  temperature  of  250°-5.  3  at- 
mospheres of  pressure  raise  the  temperature  to  275°,  4  to 
293°-7,  5  to  307°,  10  to  358°,  15  to  392°-5,  20  to  418°-5, 
25  to  439°,  30^0457°,  40  to  486°,  and  50  atmospheres 
raise  it  to  510°.  Perkins  heated  steam  so  highly  that  a 
jet  of  it  set  fire  to  combustible  bodies. 


135.  Explain  the  pulse-glass.  What  practical  application  is  made  of 
these  principles?  136.  What  is  Papin's  digester?  What  Marcet'd? 
What  relation  is  there  between  boiling  points  and  pressure  ? 


VAPORIZATION. 


91 


The  clastic  power  of  steam  in  con- 
tact with  water  is  limited  only  by 
the  strength  of  the  containing  ves- 
sel ;  but  if  steam  alone  be  heated 
without  water,  then  its  elastic  or 
expansive  power  is  exactly  like  that 
of  other  gases  or  vapors.  M.  de  la 
Tour  has  shown  that  many  liquids 
may  be  entirely  converted  into  va- 
por in  a  space  but  little  greater  than 
their  own  volume. 

137.  The  increase  of  volume  in 
changing  from  a  liquid  to  a  gaseous 
state  is  such,  that  1  cubic  foot  of 
water  becomes  nearly  1700   cubic 
feet  of  steam;  or,  in  whole  num- 
bers, a  cubic  inch  of  water  becomes 
nearly  a  cubic  foot  of  steam  ;  while 
1  cubic  foot  of  alcohol   and  ether 
yield  respectively  493  and  212  cubic 
feet  of  vapor.     The  latent  heat  of 
steam  diminishes  as  the    sensible 
heat  rises,  so  that  the  heating  power 
of  steam  at  400°  is  no  greater  than 
that  of  an  equal  volume  at  212°. 
On  the  other  hand,  the  latent  heat 
of  steam  produced  at  low  tempera- 
tures, as  in  a  partial  vacuum,  in- 
creases as  the  sensible  heat  falls. 
Hence  there  is  no  fuel  saved  by  dis-  ~; 
tilling  in  vacuo.     There  is  a  con- 
stant ratio  between  the  "latent  and  Flg>  11L 
sensible  heat  of  steam;  the  two  added  together  always  give 
the  same  sum.   Thus,  steam  at  212°  has  latent  heat  =  972°; 
giving  the  sum  1184°.    Subtract  the  sensible  heat  of  steam 
at  any  temperature  from  the  constant  number  1184,  and  we 
have  the  latent  heat  for  that  temperature,  e.  g.  steam  at 
280°  has  a  latent  heat  of  904°.     So,  also,  at  100°,  steam 
has  1084°  of  latent  heat. 

138.  Equal  volumes  of  different  vapors  contain  equal  quan- 
tities of  latent  heat.     By  iceiylit,  water  vapor  has  about  twice 


What  was  DC  la  Tour's  observation?     137.  What  is  the  dilatation  of 
eteain  ?     What  relation  between  sensible  and  latent  heat? 


92 


HE,\T. 


Fig.  112. 


and  a  half  more  latent  heat  than  alcohol  vapor,  (972 : 385;) 
but  the  specific  gravity  of  alcohol  vapor  is  about  2-5  times 
greater  than  that  of  water-vapor,  (1590  :  622.) 
Consequently,  if  the  same  expenditure  of  heat 
produces  from  all  vapors  the  same  bulk  of 
vapor  having  equal  quantities  of  latent  heat, 
there  can  be  no  advantage  in  substituting  any 
other  fluid  for  water  as  a  source  of  vapor  in 
the  steam-engine. 

139.    The  Steam- Engine. — The    principle 
of  this  apparatus  is  simple,  and  easily  illus- 
trated by  the  little  instrument  contrived  by 
Dr.  Wollaston,  (fig.  112.)    A  glass  tube,  with 
a  bulb  to  hold  a  little  water,  is  fitted  with  a 
piston.     A  hole  passes  from  the  under  side 
through  the  rod,  and  is  closed  by  a  screw  at  a. 
This  screw  is  loosened  to  admit  the  escape  of 
the  air,  and  the  water  is  boiled 
over  a  lamp :  as  soon  as  the  steam 
issues  freely  from  the  open  end  of 
the  rod,  the  screw  is  tightened, 
and  the  pressure  of  the  steam  then 
raises  the  piston  to  the  top  of  the 
tube  ;  the  experimenter  withdraws 
it  from   the  lamp,  the  steam  is 
condensed,  and  the  air  pressing 
freely   on  the   top  of  the  piston 
forces  it  down   again;   when  the 
operation  may  be  repeated  by  again 
bringing  it  over  the  lamp. 

In  the  common  condensing  en- 
gine (fig.  113)  a  cylinder  a  is 
fitted  with  a  solid  piston,  the  rod 
of  which  moves  through  a  tight 
packing  in  the  cover,  and  to  it  the 
machinery  is  attached.  A  pipe 
d  brings  the  steam  from  a  boiler 
to  the  valve  arrangement  c  by 
which  the  steam  is  admitted,  alter- 
nately, to  the  top  and  bottom  of 


Fig.  113. 


138.  What  of  equal  volumes  of  different  vapors?  Compare  alcohol 
and  water.  139.  What  is  Wollaston's  toy?  Give  the  principle  of  thi 
Btearu-engine  in  fig.  112. 


VAPORIZATION  93 

the  cylinder ;  and  also  an  alternate  communication  is  opened 
with  the  condenser  b.  Thus,  when  the  steam  enters  at  the 
top,  (in  the  direction  of  the  arrow,)  that  at  the  bottom  of 
the  piston  is  driven  through  the  lower  opening  to  6,  where 
it  is  condensed.  The  valves  are  moved  at  the  proper  time 
by  the  machinery. 

140.  Evaporation  from  the  surface  of  liquids  takes  place 
at  all  temperatures.     Even  snow  and  ice  waste  by  evapora 
tion,  at  temperatures  much  below  32°.     Mercury  rises  in 
vapor  even  at  the  temperature  of  60°.     Faraday  found  at 
that  temperature  that  a  slip  of  gold-leaf  suspended  in  a 
vacuum  over  mercury  was,  in  a  few  hours,  whitened  by  amal- 
gamation with  the  vapor  of  that  metal.     The  state  of  the 
atmosphere  as  to  dryness  and  pressure  influences 
natural  evaporation,  which  is  greatly  increased  by 

heat  and  a  rapid  wind.  It  must  be  remembered 
that  all  the  water  which  falls  to  the  earth  in  snow 
and  rain  has  arisen  in  evaporation.  That  natural 
evaporation  takes  place  only  from  the  surface  is 
proved,  by  its  being  entirely  prevented  by.  a  film 
of  oil  on  the  fluid. 

141.  Influence  of  Pressure  on  Evaporation. — If 
we  introduce  a  few  drops  of  water  into  the  vacuum 
above  the  mercury  in  a  barometer  tube,  a  part  of 
it  will  be  vaporized,  and  the  level  of  the  mer- 
cury will  be  correspondingly  reduced.    The  tension 
of  the  vapor  is  increased  by  an  elevation  of  tem- 
perature.    A  larger  tube  may  be  placed  over  the 
barometer  tube,  the  lower  end  of  which  dips  under 
the  mercury,  and  we  may  then  fill  the  intervening 
space  with  hot  water,  (fig.  114.)     The  vapor  of 
the  confined  water  will  force  down  the  column  of 
mercury  in  direct  proportion  to  the  temperature ; 
and,  by  means  of  a  thermometer  and  a  scale  of 
inches,  we  can  tell  exactly  the  tension  of  the  vapor 
of  water  for  every  temperature  under  212°. 

142.  Maximum  Density  of  Vapors. — Into  the 
torricellian  vacuum  introduce  a  portion  of  sulphuric 
ether:   a  part  of  it  is  instantly   converted    into 
vapor,  and   the   mercury   depressed   thereby  to      s' 114:* 

140.  What  of  natural  evaporation?    141.  What  influence  has  pressui* 
on  evaporation? 


94 


HEAT. 


about  14  inches.  If  we  have  a  deep  cistern,  as  in  fig.  115, 
in  which  we  can  depress  the  tube  by  the  pressure  of  the 
hand,  it  will  be  seen  that  the  film  of  liquid 
on  the  surface  of  the  mercury  increases  as  the 
tube  descends,  until  the  vapor  of  ether  is 
at  last  entirely  converted  to  the  fluid  state. 
On  withdrawing  the  hand,  the  ether  again 
flashes  into  vapor.  There  is  then,  it  is  plain, 
a  point  of  density  (or  pressure)  for  the  vapor 
of  ether,  which  cannot  be  passed  without  again 
converting  it  to  a  liquid.  This  is  true  of  all 
volatile  liquids;  and  this  point  is  called  the 
maximum  density  of  vapors.  The  weight 
of  100  cubic  inches  of  water  vapor  at  212°  is 
14-962  grains,  while,  at  32°,  the  same  volume 
of  vapor  of  water  is  only  0-136.  The  point 
of  maximum  density  of  a  vapor  is  lowered  by 
cold  as  well  as  by  pressure,  and  when  these 
two  effects  are  united,  we  can  convert  many 
gases,  which  are  quite  permanent  at  the  com- 
mon pressure  and  temperature  of  the  air,  into 
liquids,  and  even  to  solids. 

143.  The  cold  produced  by  evaporation  is 
owing  to  the  assumption  of  heat  by  the  newly 
formed  vapor.   Availing  ourselves  of  this  prin- 
ciple, water  may  be  frozen  by  the  evaporation 
of  ether,  even  in  the  open  air.     Leslie  showed 
that  water  might  be  frozen  by  its  own  evapo- 
ration, as  in  the  experiment  figured  in  the  mar- 
gin, (fig.  116.)     Water  is  contained  in  a  shal- 
low capsule  supported  by  a  tripod  of  wire 
over  a  dish  containing  sulphuric  acid,  and 
the  whole  is  covered  by  a  low  air-jar.     On 
working  the  pump,  the  water  eva- 
porates so  rapidly  in  the  vacuum 
as  to  boil  even  at  72°  :  its  vapor 
is  instantly  absorbed  by  the  sul- 
phuric acid,  and  in  this  way  both 
Fig.  116.  the  sensible  and  latent  heat  are 

removed  so  rapidly  that  the  water  is  frozen,  while  still  ap- 
parently boiling. 


Fig.  115. 


142.  What  is  meant  by  maximum  density  of  vapors  ?     143.  Whence 
iho  cold  of  evaporation  ?     What  is  Leslie's  experiment  ? 


VAPORIZATION.  95 

The  Cryophorus,  or  frost-bearer,  offers  another  illustration 
of  the  same  principles.  This  instrument,  invented  by  Dr. 
"Wollaston,  consists  of  two  glass  bulbs  blown  upon  the  same 
tube(fig.H7): 
one  of  them 
contains  a  lit- 
tle water;  the 
space  over  the 
water  is  a  va-  lS-  ' 

cuum,  the  tube  having  been  sealed  when  the  water  was 
boiling.  On  placing  the  empty  bulb  in  a  freezing  mix- 
ture, the  vapor  of  water  is  so  rapidly  condensed  as  to  freeze 
the  fluid  in  the  ball  which  is  remote  from  the  freezing 
mixture,  and  which  is  usually  protected  by  an  envelope  of 
muslin. 

144.  Dew- Point. — If  we  drop  bits  of  ice  into  a  tumbler 
of  water  (one  of  polished  silver  is  best)  having  the  same 
temperature  with  the  air,  and  watch  the  fall  of  a  thermo- 
meter placed  in  it,  we  can  denote  with  accuracy  the  temper- 
ature of  the  water,  when  it  has  cooled  so  far  that  moisture 
begins  to  be  deposited  on  the  clean  surface  of  the  glass. 
This  temperature  is  called  the  dew-point;  and  the  number 
of  degrees  between  it  and  the  temperature  of  the  air  is  an 
accurate  indication  of  the  actual  dryness  of  the  air.  In 
this  climate,  in  summer,  this  difference  amounts  often  to 
40°  or  more,  and  in  India  it  has  been  known  to  be  as  much 
as  61° ;  that  is,  with  an  external  temperature  of  90°,  the 
dew-point  has  been  seen  as  low  as  29°.  The  amount  of 
moisture  in  the  air  has  an  influence  on  the  indications  of 
the  barometer,  and  it  is  always  requisite,  in  making  baro- 
metrical observations,  to  make  a  correction  for  the  tension 
of  the  vapor  of  water  in  the  air. 

Several  common  facts  are  explained  by  a  reference  to  these 
principles.  When  the  air  is  highly  charged  with  humidity, 
it  deposits  dew  on  any  substance  colder  than  itself.  A  glass 
of  iced  water  in  summer  is  immediately  covered  with  a  coat  of 
condensed  vapor;  when  a  warm  humid  morning  succeeds  a 
cool  night,  we  see  the  pavements  and  walls  of  the  houses 
reeking  with  deposited  water,  as  if  they  had  been  drenched 
with  rain.  The  fall  of  dew  (as  has  been  already  explained) 

Describe  the  cryophorus.  144.  What  is  the  dew-point  ?  How  observed  ? 
What  common  facts  are  explained  by  it  ? 


HEAT. 


occurs  in  consequence  of  the  radiation  from  the  earth  re 
ducing  its  temperature  below  the  "  dew-point." 

145.  Hygrometers  are  instruments  to  determine  the 
amount  of  moisture  in  the  air.  One  much  used  is  called 
the  wet  lulb  hygrometer,  (fig.  118,)  or  psychro- 
meter,  and  consists  of  two  similar  delicate  mer- 
curial thermometers,  the  bulb  of  one  of  which  is 
covered  with  muslin  and  is  kept  constantly  wet 
by  water,  led  on  to  it  by  a  string  from  a  tube  in 
the  centre.  The  evaporation  of  the  water  from 
the  wet  bulb  reduces  the  temperature  of  that 
thermometer  to  which  it  is  attached,  in  propor- 
tion to  the  dryness  of  the  air,  and  consequent 
rapidity  of  evaporation.  The  other  thermometer 
indicates  the  actual  temperature ;  and  the  differ- 
ence being  noted,  a  mathematical  formula  ena- 
bles us  to  determine  the  dew-point. 

146.  But  a  much  more  delicate  instrument  for 
this  use  is  that  of  Mr.  Daniell,  which  is  con- 
structed on  the  principle  of  the  cryophorus,  (143.) 
It  is  represented  in  fig.  119.  The  long  limb 
ends  in  a  bulb,  which  is  made  of  black  glass,1  that 
Fig.  118.  ^he  condensed  vapor  may  be  more  easily  seen 
on  it.  It  contains  a  portion  of  ether,  into  which  dips  the 
6all  of  a  small  and  delicate  thermometer  contained  in  the 
cavity  of  the  tube.  The  whole  instrument  contains  only 
the  vapor  of  ether,  air  having  been  removed.  The  short 
limb  carries  an  empty  bulb,  which  is 
covered  with  muslin.  On  the  support  is 
another  thermometer,  by  which  we  can 
observe  the  temperature  of  the  air.  When 
an  observation  is  to  be  made  by  this  in- 
strument, a  little  ether  is  poured  on  the 
muslin  :  this  evaporates  rapidly,  and  of 
course  reduces  the  temperature  of  the 
other  ball.  As  soon  as  this  has  fallen 
to  the  dew-point,  the  moisture  collects 
and  is  easily  seen  on  the  black  glass. 
At  this  instant,  the  temperature  indicated 
Fig.  119.  j^  the  two  thermometers  is  noted,  and 


145.  "What  are  hygrometers  ?     Describe  the  wet  bulb.     146.  Describe 
Daniell's.    What  is  the  principle  of  Daniell's?    Which  is  the  best? 


VAPORIZATION. 


97 


tb«,  difference  gives  us  the  true  dew-point.  The  latest  and 
most  improved  form  of  hygrometer  is  that  of  Ilegnault :  it 
involves  the  principle  of  Daniell's,  with  important  means  of 
additional  accuracy. 

147.  Diffusion  and  Effusion  of  Gases  and  Vapors. — The 
vapor  of  water  will  rise  and  fill  a  confined  vessel  of  air,  and 
have  the  same  tension  as  if  no  air  were  present.     It  will 
take  a  longer  time  to  do  it,  but  as  much  will  ultimately  rise 
as  if  the  space  were  a  vacuum.     The  air  seems  to  be  an 
impediment  only  to  the  rapid  rise  of  the  vapor.     On  the 
same  principle,  probably,  is  explained  the  curious 

and  important  fact,  that,  when  different  gases  are 
in  contact,  they  will  not  remain  separate,  but  will 
soon  mingle  uniformly,  even  against  the  force  of 
gravity.  Our  atmosphere,  for  instance,  is  composed 
of  two  gases,  the  specific  gravities  of  which  are  as 
976  to  1130,  and  we  might  suppose  that  the  heavier 
would  be  at  the  bottom,  as  would  be  the  case  in  two 
such  liquids  as  water  and  oil.  But  they  are  found 
to  be  in  a  state  of  uniform  mixture.  If  we  connect 
together  by  a  narrow  tube  two  bottles,  (fig.  120,) 
containing,  one  a  light  gas,  hydrogen,  and  the  other 
a  heavier  gas,  oxygen,  and  place  the  heavy  one 
uppermost,  in  a  few  hours  we  shall  find  them  per- 
fectly commingled;  as  may  be  proved  by  the  fact 
that  the  mixture  will  explode  violently  on  touching  Fi£- 12°- 
a  match  to  the  open  mouth  of  one  of  the  vessels, 
which  we  know  a  mixture  of  these  two  gases 
will  always  do. 

148.  If  we  fill   the  end  of  a   glass   tube 
(fig.  121)  of  moderate  size  with   a  plug  of 
plaster   of    Paris,   we   form    what    is    called 
Graham's  diffusion  tube.     When  the  plaster 
is  dry,   if    the  tube    be   filled,  for   example, 
with   hydrogen  gas,   and  its  open  end  intro- 
duced into  a  vessel  of  water,  this  liquid  is 
seen  to  rise  rapidly,  owing  to  the  escape  of 
the  light  gas  into  the  air.     At  the  same  time 
the  air  enters  the  tube,  and  renders  the  mix- 
ture explosive ;    but  nearly  four  volumes  of      Fig.  121. 


147.  What  is  meant  by  diffusion  of  gases  ?     Give  an  illcutration.     148. 
A'hat  is  the  diffusion  tube  ?     In  what  proportion  does  the  air  enter? 


98  HEAT. 

hydrogen  escape  for  one  of  air  which  enters,  and  these  are 
called  the  diffusion  volumes  of  hydrogen  and  air.  Every 
gas  has  its  own  diffusion  volume  depending  on  its  density, 
these  being  inversely  as  the  square  root  of  the  densities  of 
the  gases.  The  same  law  pertains  to  the  rapidity  with  which 
gases  rush  into  a  vacuum  through  a  minute  orifice. 

149.  The  passage  of  gases  through  moist  membranes  is 
connected  with  this  subject,  but  involves  also  another  con- 
dition, viz.  the  solubility  of  certain  gases  in  water.     For 
example,  a  bladder  partly  full  of  air,  and  tied  tightly  at  the 
neck,  is  introduced  into  an  air-jar  full   of  carbonic  acid ; 
after  some  hours  the  bladder  is  found  much  distended,  and 
may  finally  burst,  from  the  passage  of  the  carbonic  acid  gas 
into  it.     This  is  effected  by  the  solubility  of  this  gas  in 
water :    it  thus  passes  the  pores  of  the  membrane,  and  is 
rapidly  diffused  again  in  the  air  of  the  bladder.   Dr.  Mitchell 
found  that  the  time  required  to  pass  the  same  volume  of 
several  gases  through  the  same    membrane  was  1  minute 
for  ammonia,  2£  minutes  for  sulphuretted  hydrogen,  3i  for 
cyanogen,  5£  for  carbonic  acid,  6J  for  nitrous  acid,  28  for 
olefiant  gas,  37  J  for  hydrogen,  113  for  oxygen,  and  160  for 
carbonic  oxyd.     For  nitrogen  the  time  was  much  greater. 

150.  Liquefaction  and  Solidification  of  Gases. — In  1823, 
Faraday  first  demonstrated  the  possibility,  by  united  cold 
and  pressure,  of  reducing  several  gases  to  the  liquid  and 
even   solid  state.      The  apparatus  originally  employed  in 
these  interesting  but  hazardous  experiments,  was  simply  a 

stout  glass  tube,  bent  as 
in  figure  122,  containing 
the  materials  to  evolve 
the  gas,  and  heated  at 
both  ends.  If  cyanogen 
122.  is  to  be  liquefied,  dry 

cyanid  of  mercury  is  placed  in  one  end  of  the  tube,  and 
heated,  while  the  empty  end  is  cooled  in  a  freezing  mixture : 
the  gas,  accumulating  in  a  narrow  space,  is  liquefied  by 
the  force  of  its  own  elasticity.  Some  hazard  attends  these 
experiments,  and  the  operator  should  be  protected  by  gloves 
and  a  mask  of  wire-gauze.  In  this  way,  chlorine,  cyanogen, 


What  is  the  law  of  diffusion  ?  149.  What  of  the  passage  of  gases 
through  membranes  ?  Give  an  example.  What  are  Mitchell's  results  ? 
lot)  Who  first  liquefied  gases  ?  What  was  the  means? 


VAPORIZATION. 


carbonic  acid,  nitrous  oxyd,  and  several  other  gases  have 
seen  reduced  to  the  liquid  state,  and  some  to  the  solid  con- 
dition. Several  of  these  gases — as  ammonia,  cyanogen,  and 
sulphurous  acid — may  be  liquefied  by  cold  alone,  without 
additional  pressure. 

151.  M.  Thitorier's  apparatus  for  liquefaction  of  carbonic 
acid  involves  the  same  principle.  In  fig.  123,  g  is  the  gene- 
rator of  the  gas,  a  strong  cast- 
iron  vessel,  hung  by  centres  on 
a  frame  f\  in  it  is  put  the 
requisite  quantity  of  carbonate 
of  soda  and  water,  and  a  tube  a 
of  copper,  holding  an  equivalent 
amount  of  strong  sulphuric  acid ; 
the  cap  of  red  metal  is  strongly 
screwed  in,  the  valve  closed, 
and  the  position  of  the  appa- 
ratus inverted,  by  turning  it 
over  on  its  centres;  the  acid 
then  runs  out  among  the  car- 
bonate of  soda,  and  an  enor- 
mous pressure  is  generated  by 
the  successive  portions  of  gas 
evolved.  After  a  time,  when  the  action  is  complete,  the 
generator  is  connected  by  a  metallic  tube  with  the  receiver 
r]  stopcocks,  simple  screw-plugs  having  a  conical  point, 
confine  the  gas,  and  being  opened,  the  liquefied  gas  collects 
in  r,  which  is  cooled  by  a  freezing  mixture  for  the  purpose 
of  condensing  it.  In  this  way,  several  successive  quarts  of 
the  liquid  carbonic  acid  gas  are  accumulated  in  r.  A  por- 
tion of  this  liquid  may  be  safely  drawn  off  into  a  strong 
glass  tube  refrigerated.  It  can  then  be  drawn  off  by  a  jet 
j  secured  to  the  top,  which  enters  a  metallic  box  b  with 
perforated  wooden  handles.  The  rapid  evaporation  of  a 
part  of  the  liquid  gas  absorbs  so  much  heat  from  the  rest, 
that  a  considerable  portion  is  converted  to  a  fine  white  solid, 
like  dry  snow,  which  fills  the  box.  When  once  solidified, 
it  wastes  away  very  slowly,  and  may  be  handled  and 
moulded  with  ease.  If  suffered  to  rest  on  the  hand,  how- 
ever, it  destroys  the  vitality  of  the  flesh,  like  a  hot  iron. 
It  is  now  in  a  condition  analogous  to  bodies  in  the  spheroidal 


Fig.  123. 


What  gases  have  been  liquefied  ?     Describe  Thilorier's  apparah 


100  ELECTRICITY. 

state  (131 ;)  being  surrounded  by  an  atmosphere  of  its  own 
vapor,  the  radiation  of  heat  to  it  from  surrounding  bodies  is 
cut  off,  and  it  acquires  the  very  low  temperature  of  — 140°, 
If  it  is  wet  with  ether  in  a  capsule  containing  mercury,  the 
latter  is  frozen  solid,  and  can  then  be  hammered  with  a 
wooden  mallet,  and  drawn  out  like  lead.  When  moistened 
with  ether  in  vacuo,  with  certain  precautions,  the  very  low 
temperature  of  — 166°  is  produced.  Carbonic  acid  at  0°  has 
a  tension  of  nearly  23  atmospheres  ;  at  32°  its  tension  is 
38£  atmospheres;  at  —84°,  12 J;  at  —75°,  4.60;  and  at 
— 111°,  1-14  atmospheres.  It  becomes  at  — 71°  a  clear 
transparent  solid,  sinking  in  the  surrounding  fluid. 

This  apparatus  once  exploded  in  Paris,  killing  the  assist- 
ant in  a  frightful  manner.  It  is,  however,  due  to  Mr. 
Chamberlain,  of  Boston,  to  say  that  the  author  has  re- 
peatedly used  several  of  these  instruments  of  his  construc- 
tion with  entire  safety. 

152.  By  the  use  of  mechanical  pressure,  and  the  enor- 
mously low  temperature  of  the  bath  of  carbonic  acid  and 
ether  in  vacuo,  Faraday  has  succeeded  in  reducing  several 
other  gases  to  the  liquid  or  solid  state.  These  facts  will  be 
mentioned  under  the  history  of  the  several  substances. 

The  greatest  artificial  cold  hitherto  observed  is  220°  below 
zero  of  Fahrenheit,  and  was  obtained  by  Natterer,  with  the 
aid  of  a  bath  of  liquid  nitrous  oxyd  and  sulphuret  of  carbon 
in  vacuo.  The  greatest  natural  cold  recorded  is  — 76°  below 
zero. 

Several  gases  have  resisted  all  attempts  to  reduce  them  to 
a  liquid  state,  viz.  hydrogen  at  27  atmospheres;  oxygen  at 
58  £ ;  nitrogen,  nitric  oxyd,  and  carbonic  oxyd  at  50,  and  coal 
gas  at  32  atmospheres,  aided  by  the  greatest  artificial  cold. 


IV.  ELECTRICITY. 

153.  More  than  600  years  B.  c.  the  ancients  observed  in 
amber  a  remarkable  power  of  excitation  by  friction.  Mo- 
dern science  has  conferred  on  this  power  the  name  of  elec- 
tricity, from  the  Greek  word  for  amber,  (electron.']  This 
force,  or  power,  has  various  modes  of  existence  or  manifesta- 


152.  How  has  Faraday  reduced  other  gases  ?  What  is  the  lowest 
temperature  observed  ?  What  in  nature  ?  What  gases  have  resisted 
liquefaction?  153.  What  was  the  first  electrical  observation? 


MAGNETIC   ELECTRICITY.  101 

tion,  which  are  chiefly,  1.  Magnetic  electricity;  2.  Erie- 
tioual,  or  statical  electricity;  3.  Dynamical,  voltaic,  or  gal- 
vanic electricity,  (from  chemical  action;)  4.  Thermo-elec- 
tricity; and,  5.  Animal  electricity. 

Magnetic  Electricity,  or  Magnetism. 

154.  Lode-stone. — A  kind  of  iron-ore  has  been  know* 
from  remote  antiquity,  that  has  the  property  of  attractir, 
to  itself  small  particles  of   iron;  this  is  called 

the  lode-stone.      By  contact,  it  can    impart   its 
virtues  to  iron  and  steel,  and  also,  to  a  consider- 
able  degree,    to    cobalt    and    nickel.      As    it 
abounded  in  Magnesia,  it  w»  called  by  Pliny 
magnes,  and  hence  the  name  magnet.     This  ore 
mounted  in  a  frame  of  soft  iron  II,  (fig.  124,) 
constituted  the   original  magnet :  pp'    are  the 
poles.     A  bar,  or  needle  of  steel,  which  has  received  the 
magnetic  influence,  when  suspended  on  a  point,       ^ 
will  be  found  to  have  a  directive  tendency, 
by  which    one    end   turns  invariably  to    the 
north.     The   needle,  therefore,  has   polarity, 
and  the  end  turning  north  is  called  the  north 
pole,  and  the  other  end  the  south  pole. 

155.  Polarity. — If  we  bring  the  north  end 
of  a  magnetic  bar  near  to  the  similar  end  of 

the  suspended  needle,  the  latter  will  move  away,  as  indi- 
cated by  the  arrows,  being  repelled  by  the  similar  power  of 
the  bar.  If,  however,  we  bring  the  end  N  - 

toward  the  opposite  end  of  the  needle  S,  it  |s  ^  •••""""'iimniiBp 
will  be  attracted  to  the  bar,  and  strive  to  move  •Flg" 126' 
as  near  to  it  as  possible.  The  reverse  is,  of  course,  true  of 
the  opposite  end  of  the  bar.  If,  in  place  of  a  magnetic  bar, 
we  had  used  a  bar  of  unmagnetic  iron,  we  should  have  found 
both  ends  of  the  suspended  needle  equally,  but  less  power- 
fully, attracted  by  it.  We  thus  learn  (1)  that  the  magnet 
has  polarity ;  and  (2)  that  poles  of  the  same  name  repel, 
and  those  of  opposite  names  attract  each  other. 

156.  Induction  of  Magnetism. — The  manner  in  which  a 
magnet,  or  lode-stone,  imparts  its  own  power  to  surrounding 

"What  modes  of  electricity  are  named  ?  154.  What  is  the  lode-stone  ? 
What  is  the  needle?  155.  What  is  polarity?  What  is  the  law  of  rfr 
pulsion?  156.  What  is  induction  ? 


It32  ELECTRICITY. 

substances,  is  called  induction,  and  thoso 
bodies  capable  of  manifesting  this  power 
are   said  to  be   magnetized  by  the  in- 
ductive  influence.     Thus,    a    series    of 
bars  of  soft  iron  laid  about  a  magnetic 
bar,  as  in  the  figure,  will  all  become 
temporarily  magnetic  by  induction  ;  and 
in    obedience  to   the   law  just  stated, 
their  ends  next  the  N  are  all  S,  and 
their  remote  ends  all  N.     Every  mag- 
Fig.  127.  nc^  go  j-0  Speak,  is  surrounded  by  an 
atmosphere  of  influence,  which  has  its  centre  in  the  poles 
of  the  magnet,  and  diminishes  in  intensity  inversely  as  the 
square  of  the  distance.     This  decrease  of  force  is 
prettily  illustrated  by  an  experiment  shown  in  the 
annexed  cut.     The  bar  magnet  holds  a  large  key ; 
this  can  hold  a  second  smaller  than  itself;  this,  a 
nail  ;  the  nail,  a  tack-nail  ;  and  lastly,  a  few  iron- 
filings  are  held  by  the  tack-nail;  and  the  whole  re- 
ceive their  magnetism  by  induction  from  the  bar, 
and  each  article  has  its  own  separate  polarity.     In- 
duction takes  place  through  a   glass-plate,  or  any 
similar  substance. 

157.  Permanent,  magnets  can  be  made  only  of 
hardened  steel.  Soft  iron  and  steel  become  mag- 
nets only  while  under  the  influence  of  other  magnets, 
and  lose  their  own  power  as  soon  as  removed  from 
them.  Magnetism  is  imparted  by  {  touch,'  as  it  is 
technically  called,  from  a  previously  existing  mag- 
net. An  unmagnetic  bar  of  hardened  steel,  when 
properly  rubbed  by  the  poles  of  a  magnet,  will  itself 
soon  acquire  polarity  and  magnetic  power.  Mag- 
Fig.  128.  netism  is  thought  to  rest  mostly  on  the  surface  of 
the  metal.  Every  magnet  is  regarded  as  made  up  of  a 
great  number  of  small  magnets,  so  to  speak,  each  particle 
of  steel  having  its  own  polarity.  We  cannot  conceive  of  one 
n  *  n  s  n  s  n  *  n  s  n  s  n  s  v  s  sort  of  polarity  existing 

cj*a  cjg  rgra  CM  c^ma  r^w  cc«a  r^sa  g   Without  the   Other.       Thus, 

aS^i^Si^ESEi  i°   figurc  129,  we  see   a 

p}o.  129  magnified     representation 


Explain  figs.  127  and  128.     157.  What  are  permanent  magnets  ?    What 
\s  attraction  and  '  touch'  ?    How  are  the  forces  in  a  magnet  distributed  ? 


MAGNETIC   ELECTRICITY.  103 

of  this  condition.  Each  little  magnet  has  its  own  n  and  *. 
Those  which  occupy  the  middle  of  the  bar,  being  acted  on 
alike  in  all  directions,  can  show  no  power ;  but  the  force 
accumulates  toward  each  end,  until  we  find  the  greatest 
power  in  the  last  range  of  particles,  which  we  term  the 
poles. 

If  we  dip  a  magnetic  bar  in  iron-filings,  we  shall  find  only 
the  ends  attracting  a  tuft  of  the  metallic  particles,  while  the 
middle  is  free.  If  two  magnetic  bars,  however,  like  the 
figure,  are  placed  together,  (-f-  and  — ,)  and  a  sheet  of 
paper  laid  over  them,  they  will  attract  iron-filings  scattered 
on  the  paper,  in  the  way 
represented  in  the  figure  : 
here  a  pair  of  central  poles 
have  power  to  attract  the 
iron,  which  the  middle 
part  of  the  simple  bar  had  Fig.  130. 

not.  The  particles  of  iron  arrange  themselves  in  what  are 
called  magnetic  curves.  These  curves  represent  very  nearly 
the  lines  of  magnetic  force  which  always  environ  a  magnet, 
and  tend  to  impart  magnetic  properties  to  all  bodies — solid, 
liquid,  or  gaseous — which  come  within  their  range. 

158.  Artificial  Magnets  are  made  of  all  forms,  the  most 
common  being  the  so-called  horse-shoe  magnet,  shaped  like 
figure  131.     It  is  found  that  the  power  of  magnets      •  • 

is  much  increased  by  uniting  several  thin  plates  of  V 
hardened  steel,  each  of  which  is  separately  magnet-  Fl£- 131- 
ized.  A  bar  of  soft  iron,  called  the  keeper,  is  placed  across 
the  poles  of  the  horse-shoe  magnet,  to  prevent  it  from  losing 
power;  and  if  it  be  made  to  hold  a  weight  nearly  equal  to 
the  power  of  the  magnet,  it  will  be  found  to  gain  strength  daily 
up  to  a  certain  point,  and  in  like  manner  to  lose  its  magnet- 
ism if  unemployed.  Artificial  magnets,  weighing  one  pound, 
have  been  made  to  sustain  28  times  their  own  weight. 

159.  The  Earth's  Magnetism. — The  earth  is  regarded  as 
a  great  magnet.     Its  power  is  equal,  according  to  Gauss,  to 
that  which  would  be  conferred  if  every  cubic  yard  of  it  con- 
tained six  one-pound  magnets.     The  sum  of  the  force  is 
equal   to    8,464,000,000,000,000,000,000    such    magnets. 
The  magnetism  which  we  see  in  bars  of  steel  and  the  lode- 


Illustrate  this  as  in  fig.  129.     158.  How  kre  magnets  formed  and  pre- 
served ?    What  is  terrestrial  magnetism  ?    What  its  force  in  a  cubic  yard? 


104  ELECTRICITY. 

stone  is  the  result  of  induction  from  the  earth.  Magnetism 
from  the  earth  is  induced  in  all  bars  of  steel  or  iron  which 
stand  long  in  a  vertical  position.  Tongs  and  blacksmiths' 
tools  are  often  found  to  be  magnetized.  A  bar  of  iron  held 
in  the  magnetic  meridian,  and  at  the  proper  inclination, 
becomes  immediately  magnetic  from  the  induction  of  the 
earth ;  and  the  effect  may  be  hastened  by  striking  it  on  the 
end  with  a  hammer :  the  vibration  seems  to  aid  in  inducing 
the  magnetic  force.  The  tools  used  in  boring  and  cutting 
iron  are  also  generally  found  to  be  magnets.  The  magnetic 
poles  of  the  earth  are  not  in  the  same  points  with  the  poles 
of  revolution  or  the  axis  of  the  earth,  and  for  this  reason 
the  magnetic  needle  does  not  point  to  the  true  north  and 
south,  but  varies  from  it  more  or  less,  and  differs  at  different 
times,  as  the  magnetic  pole  alters  its  position.  This  is 
called  the  variation  of  the  needle. 

160.  Dipping  Needle. — The  magnetism  of  the  earth  is 
beautifully  shown  by  the  dipping  needle,  represented  in  the 

annexed  figure.  The  needle  n  is  sus- 
pended on  the  horizontal  bar  a,  so  as 
to  move  in  a  vertical  plane,  instead  of 
horizontally,  as  in  the  compass-needle. 
The  graduated  vertical  circle  c  is  placed 
in  the  magnetic  meridian,  and  the  needle 
then  assumes,  in  this  latitude,  (41°  18',) 
the  position  shown  in  the  figure,  dipping 
Fig.  132.  at  an  angle  of  73°  27'.  Over  the  mag- 
netic equator  it  would  stand  horizontal,  being  equally  at- 
tracted in  both  directions.  At  either  magnetic  pole  it  would 
be  vertical.  The  horizontal  variation  of  the  needle,  its  dip, 
and  the  intensity  of  the  polar  attraction,  are  subject  to  daily 
and  local  changes,  from  the  fluctuations  of  temperature  in- 
fluencing the  magnetic  conditions  of  the  atmosphere,  as 
shown  by  the  late  results  of  Faraday. 

161.  Magnetics  and  Diamagnetics. — Dr.  Faraday,  in  1845, 
made  the  important  discovery  that  all  solid  and  liquid  sub- 
stances, and  many  gases,  were  subject  to  the  magnetic  in- 
fluence.    According  to  his  results,  confirmed  by  numerous 
subsequent  observers,  all  bodies  may  be  subdivided  into  two 
great  classes — the  magnetic  and  diamagnetic.     To  the  first 

How  are  objects  affected  by  it?    Where  are  the  magnetic  poles  ?    160. 
What  is  the  dipping  needle  ?    What  is  said  of  variations  in  dip,  <fec.  ? 


ELECTRICITY   OF   FRICTION.  105 

class  belong  all  bodies  which  act  like  iron  and  nickel — that 
is,  which  place  themselves,  when  suspended  as  a  needle, 
axiatty  or  in  the  line  connecting  the  poles  of  a  magnet — 
and  which  also  exhibit  the  familiar  mode  of  attraction  by 
either  pole  of  a  magnet  alike.  The  bodies  belonging  to  this 
class  are  either  metals  or  oxyds  and  salts  of  metals,  (both 
solid  and  liquid.)  To  the  second  class  belong  all  liquids 
and  solids  which  do  not  belong  to  the  magnetic  class.  Bis- 
muth appears  to  be  the  most  remarkable  substance  in 
diamagnetic  energy.  A  suspended  needle  of  this  metal 
places  itself  at  right  angles  to  that  position  which  iron 
assumes  under  the  same  circumstances.  A  few  bodies  of 
each  class  are  enumerated  in  the  following  list,  where  we 
observe  that  iron  and  bismuth  are  at  the  extremes,  each 
standing  as  the  type  of  its  own  class,  while  air  and  vacuum 
occupy  the  zero,  or  neutral  point  of  quiescent  inactivity  : — 
Iron,  nickel,  cobalt,  manganese,  palladium,  crown-glass, 
platinum,  osmium,  — 0°,  air  and  vacuum,  arsenic,  ether, 
alcohol,  gold,  water,  mercury,  flint-glass,  tin,  heavy  glass, 
antimony,  phosphorus,  bismuth.  It  is  a  curious  sight  to  see 
a  piece  of  wood,  or  of  beef,  or  an  apple,  or  a  bottle  of  water, 
repelled  by  a  magnet;  or,  taking  the  leaf  of  a  tree  and 
hanging  it  up  between  the  poles,  to  observe  it  take  an 
equatorial  position. 

162.  The  latest  results  of  Faraday  show  that  oxygen  gas 
is  to  be  reckoned  as  a  magnetic,  having  about  2|gth  part  the 
capacity  of  iron  for  magnetic  induction.     This  fact  connects 
itself  in  the  most  important  manner  with  the  magnetic  con- 
dition of  the  atmosphere — the  daily  variations  in  dip  and 
intensity — as  probably  also  with  the  aurora  borealis. 

Electricity  of  Friction,  or  Statical  Electricity. 

163.  Statical  electricity  is  evolved  by  several  of  the  same 
causes  which  we  have  named  as  sources  of  heat.     Friction 
excites  it  abundantly  •    chemical  action  still  more  so.     It 
attends  animal  life,  and  is  powerfully  exhibited  in   some 
animals,  as  in  the  torpedo  and  electrical  eel :  heat  evolves 
it,  as  in  the  mineral  tourmalin;    and  we   have  reason  to 


161.  What  are  magnetics  and  diamagnetics?  Name  some  of  them.  162. 
What  is  Faraday's  discovery  regarding  oxygen?  163.  What  are  source* 
of  frictional  electricity  ? 


106  ELECTRICITY. 

believe  that  the  sun's  rays  are  perpetually  exciting  electrical 
currents  in  the  earth.  Like  heat,  it  neither  adds  to  nor  sub- 
tracts from  the  weight  of  matter ;  but,  unlike  heat,  it  pro- 
duces no  change  in  dimensions,  and  does  not  affect  the  power 
of  cohesion  in  bodies.  In  powerful  discharges,  however,  it- 
overcomes  cohesion  by  rending  or  fusion.  All  matter  is 
subject  to  its  influence,  and  it  can  be  transferred  from  an 
excited  body  to  one  previously  in  a  neutral  state. 

We  shall  treat  this  curious  and  most  interesting  subject 
very  briefly,  as  its  chemical  relations  are  much  more  limited 
than  those  of  galvanism. 

164.  Electrical  Excitement. — If  we  briskly 
rub  a  glass  tube  with  warm  and  dry  silk,  and 
bring  it  near  to  any  light  substance,  as  some 
Fio-  133  ^  pith,  on  the  table,  (fig.  133,)  a  flock  of  cot- 
ton, some  shreds  of  silk,  or,  as  in  fig.  134, 
to  two  balls  of  pith  suspended  on  a  hook  by  delicate  wire, 
the  light  substances  will  at  first  be  strongly  attracted  to  the 
tube,  but  in  an  instant  will  fly  from  it,  as  if 
repelled  by  some  unseen  force ;  and  any  further 
effort  to  attract  them  to  the  excited  glass  will 
,  only  cause  their  continued  removal.  Each  se- 

/     1   \.  parate  thread  of  silk  and  each  pith-ball  seems 
O     Ik     ^  to  retreat  as  far  as  possible  from  the  glass  tube 


glass  tube,  we  use  a  stick  of  sealing-wax  rubbed 
with  dry  flannel,  and  present  this  to  the  light  substances 
which  have  been  excited  by  the  glass  tube,  we  shall  find  a 
very  strong  attraction  manifested  between  them  :  the  light 
substance  previously  excited  by  the  glass  will  move  to  the 
excited  resin  much  more  actively  than  a  substance  not  pre- 
viously excited  in  this  way ;  and  two  substances  separately 
excited,  one  by  the  glass  and  the  other  by  the  resin,  will 
attract  each  other  with  equal  power.  The  first  of  these  is 
called  vitreous,  and  the  second  resinous  electricity.  These 
simple  phenomena  form  the  basis  of  all  electrical  science. 

165.  Electrical  Polarity. — There  is  a  strong  analogy  be- 
tween the  two  sorts  of  electrical  excitement  and  the  opposite 
powers  of  the  magnet.  The  vitreous  is  to  the  resinous  elec- 


"VVhat  similarity  has  it  to  heat?     What  differences  ?     164.  How  do  you 
excite  a  glass  tube  ?     How  does  it  affect  pith-balls,  <fec.  ?     How  if  wax  \» 
165.  What  is  electrical  polarity  ? 


ELECTRICITY   OF   FRICTION. 


107 


135. 


tricity  as   the   north 

pole  of  a  magnet  is 

to  the  south.     Hence 

we  call  the  vitreous 

the    positive   electri- 

city, and  the  resinous  the  negative  electricity.     A  vow  of  pith- 

balls,  (fig.  135,)  when  excited  by  induction,  or  influence,  stand 

related  to  each  other  as  shown  by  the  signs  plus  and  minus. 

166.  Electrical  machines  are  constructed  for  the  easy  ex- 
citation of  large  quantities  of  electricity.  Two  forms  of 
this  machine  —  the  cylinder 
and  the  plate  —  are  in  com- 
mon use.  In  the  plate  ma- 
chine, (fig.  136,)  c  k  is  a 
wheel  of  plate-glass,  turned 
on  an  axis  by  a  handle  m. 
The  electricity  is  excited  by 
the  friction  of  two  cushions 
or  rubbers  pressing  against 
the  plate,  and  covered  with 
a  soft  amalgam  of  mercury, 
tin,  and  zinc,  which  greatly 
heightens  the  effect.  The  "  Fig.  136. 

rubbers  are  connected  with  the  earth  by  a  metallic  chain. 
The  excited  glass  delivers  its  electricity  to  several  sharp 
points  of  wire  attached  to  the  bright  brass  arms  ii,  and 
connected  with  the  great  conductors  f  g.  The  conductors 
are  perfectly  insulated  by  glass  supports  li  h. 

In  the  cylinder  machine,  (fig.  137,)  a  hollow  cylinder  of 
glass  v  is  used,  to  excite  the  electricity  ;  c  is  the  rubber, 
and  a  r  are  the  prime 
conductors.  When 
the  winch  is  turned, 
bright  sparks  of  a 
violet  color,  form- 
ing zigzag  lines  like 
lightning,  dart  with 
a  sharp  sound  to  any 
conducting  substance 
brought  near  to  the  FiS- 


How  is  it  like  magnetic?     1C6.  What  is  the  plate  machine  ?    What  thb 
cylinder  ?     Describe  figs.  136  and  137. 


108 


ELECTRICITY. 


great  conductors.  This  is  positive  electricity.  If  negative 
electricity  be  wanted,  we  must  insulate  the  rubbers,  and, 
3onnecting  the  opposite  conductor  with  the  earth,  draw  tho 
sparks  from  the  rubber.  For  this  purpose,  the  construction 
in  fig.  137  is  most  convenient.  Every  care  must  be  taken, 
in  the  use  of  an  electrical  apparatus,  to  keep  it 
clean  and  smooth,  and  particularly  free  from  moist- 
ure. Warm  flannel  or  silk  is  to  be  used  to  wipe  the 
surface. 

167.  Electroscopesj  or  Electrometers. — The  quad- 
rant electroscope  (fig.  138)  is  usually  attached  to  the 
prime  conductor,  to  indicate  the  activity  of  the  ma- 
chine by  the  more  or  less  elevated  angle  assumed 
by  the  arm.     The  pith-balls  of  fig.  135  answer  the 
Fig.  138.  same  purpose,  and  may  also  denote  the  Idnd  of  excite- 
ment.   For  example,  if  they  are  excited  by  glass, 
on  approaching  them  with  another  excited  body, 
if  they  are  attracted,  then  we  know  that  the 
second  body  has  negative  excitement — if  re- 
pelled, positive  excitement  is  found. 

The    gold-leaf    electrometer   (fig.  139,)  is, 
however,  a  much  more  delicate  test  of  electri- 
cal excitement.     It  consists  of  two  leaves  of 
gold,  suspended  in  an  air-jar,  and  communi- 
cating by  a  wire  with  a  small  plate  of  brass ; 
the  approach  to  this  plate  of  a  body  in  any 
degree   excited,   will    occasion   an    immediate 
movement  of  the  gold-leaves,  from  which  we 
can  tell  the  nature  of  the  excitement,  as 
above  described,  having  previously  imparted 
to  the  gold-leaves  a  particular  kind  of  elec- 
tricity. 

1 68.  ColomVs  torsion  electrometer,  (fig. 
140,)  allows  of  the  exact  measurement  of 
quantities  of  electricity.  A  slender  rod  of 
gum-lac  </,  with  ends  of  gilt  pith,  is  suspend- 
ed within  a  glass  shade  a  by  a  filament  of 
glass  depending  from  the  tube/.  Another 
bar  of  lac,  also  with  gilt  pith- balls,  (called 
Fig.  140.  the  carrier-bar,)  is  introduced  at  pleasure 


Fig.  139. 


What  is  an  electroscope?    Describe  the  gold-leaf.     168.  Describe  Ca- 
lomb's  electrometer,  fig.  140.     "What  does  it  enable  us  to  do  ? 


ELECTRICITY   OF   FRICTION.  109 

by  an  opening  o  in  the  cover  of  the  instrument.  By  a  screw 
t  at  top  the  needle  may  be  adjusted.  When  unexcited,  the 
needle  and  carrier-bar  stand  in  close  proximity.  To  mea- 
sure electricity  by  this  instrument,  the  lower  ball  of  the 
carrier-rod  is  charged  and  introduced  into  the  cylinder.  It 
will  repel  the  movable  ball  in  proportion  to  the  intensity  of 
the  charge  ;  and  by  turning  the  milled  head  at  m  we  may 
measure  the  degree  of  deflection,  or  torsion,  of  the  thread 
of  glass.  This  we  can  also  note  on  the  graduated  circle  upon 
the  cylinder. 

169.  Conductors    and   Insulators    of  Electricity.  —  The 
pith-balls  or  glass  tubes,  which  have  been  electrically  ex- 
cited, return  to  a  natural  state  very  slowly  indeed,  if  left 
untouched,  in  dry  air.     But  the  hand,  or  a  metallic  rod, 
will  at  once  restore  them  to  the  unexcited  state,  while  dry 
silk,   glass,    and   resin   will    not   remove   the    excitement. 
Bodies  are,  therefore,  divided  into  conductors  and  non-con- 
ductors of  electricity,  or,  more  properly,  into  good  and  bad 
conductors.     The  electrical  discharge  takes  place  through 
good    conductors   (as  the    metals)   with    an    inconceivable 
velocity,  which  can   be  compared  only  to  the  velocity  of 
light.     Among  good  conductors,  in  the  order  of  their  con- 
ducting power,  are   the   metals,  charcoal,  plumbago,  and 
various  fused  metallic  chlorids,  st*v,ng  acids,  water,  damp  air, 
vegetable  and  animal  bodies  ;  among  bad  or  imperfect  con- 
ductors are  spermaceti,  glass,  sulphur,  fixed  oils,  oil  of  tur- 
pentine, resin,  ice,  diamond,  and   dry  gases.     The    latter 
substances  are  also  called  insulators,  because  by  their  aid  we 
«an  insulate  or  confine  electricity. 

170.  The  distribution  of  electricity  in  an  excited  body  is 
apon  the  surface.     In  proof  of  this,  if  on   the  insulated 
jtand  b  (fig.  141)  we  excite  a  spherical 

body  c  c,  provided  with  glass  handles, 

we  may  separate  its  halves  and  observe 

that  the  inner  sphere  a  has  no  excite- 

ment whatever.     All  the   electricity  _ 

remains  on  the  outer  surface.     If  the  tfig.  ui. 

body  is  egg-shaped,  the  excitement  becomes  more  concen- 

trated in  the  extremities.     A  small  point  at  the  end  of  the 

prime  conductor  will  convey  off  all  the  excitement  of  a  power- 


169.  What  are  conductors  and  insulators  ?  Name  some  of  each.  170. 
is  electricity  distributed  ?     Describe  fig.  141.     What  is  true  of  a  point  on 
the  prime  conductor  ? 


110  ELECTRICITY. 

ful  machine  insensibly,  unless  in  the  dark,  when  a  track  of 
light  will  be  seen  proceeding  from  the  point. 

The  excitement  of  a  powerful  machine  may  be 
withdrawn  by  pith-balls,  or  figures  of  pith  ar- 
ranged as  is  figure  142,  which  convey  away  the 
electricity  as  fast  as  it  is  produced — being  at- 
tracted and  repelled  between  the  two  surfaces. 

171.  Lightning  conductors  were   devised  by 
Dr.  Franklin,  after  his   memorable    experiment 
with  the  kite,  by  which  he  proved  the  identity  of  j 
atmospheric  electricity  with  that  of  machine  ex- 
citation.     The  efficacy  of  lightning  conductors, 

now  so  general,  depends  on  the  power  of  a  point  to  d*aw 
away  insensibly  very  powerful  charges  of  electricity.  It  is 
essential  that  they  should  be  well  insulated,  and  that  the 
lower  end  should  enter  so  deep  into  the  earth  as  always  to 
be  in  damp  ground. 

172.  Two  theories  have  been   proposed   to  explain  the 
ordinary  phenomena  of  electricity.     The  first  is  called  the 
Franklinian   hypothesis,   proposed    by    our    distinguished 
countryman,  Dr.  Franklin.     It   supposes    that  there  is  a 
simple,  subtle,  and  highly-elastic  fluid,  which  pervades  all 
matter.     This  fluid  is  self-repellent,  but  attracts  all  matter, 
or  its  ultimate  particles.     In  the  natural  state  of  bodies, 
this  fluid  is  uniformly  distributed  over  them,  and  its  in- 
crease or  diminution  produces  electrical  excitement.     Ac- 
cordingly, when  a  glass  tube  is  rubbed  with  a  silk  hand- 
kerchief, the  electrical  equilibrium  is  disturbed,  the  glass 
acquires  more  than  its  natural  quantity,  and  is  over-charged, 
the  silk  possesses  less,  and  is  under-charged. 

The  second  hypothesis  is  that  of  Du  Fay,  who  assumes  that 
electrical  phenomena  are  due  to  two  highly  elastic,  impon- 
derable fluids,  the  particles  of  which  are  self-repellent,  but 
attractive  of  each  other.  These  two  fluids  exist  in  all  un- 
excited  bodies  in  a  state  of  combination  and  neutralization, 
when  no  electrical  phenomena  are  seen.  Friction  occasions 
the  separation  of  the  fluids,  and  the  electrical  excitement  in 
a  body  continues  until  an  equal  amount  of  opposite  electri- 
city to  that  excited  has  been  restored  to  it. 

How  do  the  dancing  figures  discharge  electricity?  171.  How  do 
lightning  conductors  act?  172.  What  is  the  Franklinian  hypothesis? 
What  is  that  of  Du  Fay  ? 


ELECTRICITY   OF   FRICTION. 


According  to  Dr.  Franklin's  theory,  the  two  states  aro 
denominated  positive  and  negative  j  according  to  Du  Fay, 
they  are  distinguished  as  vitreous  and  resinous. 

Whichever  theory  we  may  adopt,  we  can  clearly  see  how 
it  is  impossible  ever  to  develop  one  electrical  condition 
without  at  the  same  time  giving  rise  to  the  other. 

173.  The  Lei/den  jar  was  invented  by  Cunaeus,  of 
Leyden,  in  1746.  By  it  the  experimenter  collects  and 
transfers  a  portion  of  the  electricity  evolved  by  his  machine, 
and  applies  it  to  the  purposes  of  experiment.  It  is  simply 
a  glass  jar,  (fig.  143,)  covered  inside  and  out  with  tin-foil  up 
to  the  line  seen  in  the  figure.  A  brass  ball 
communicates  by  a  wire  and  chain  with  the  in- 
terior coating,  the  mouth  being  stopped  by  a 
cover  of  dry  wood.  On  approaching  the  ball 
to  the  conductor  of  the  electrical  machine, 
when  in  action,  a  series  of  vivid  sparks  will  be 
received  by  it,  and  a  great  accumulation  of 
vitreous  electricity  takes  place  in  the  interior, 
provided  the  exterior  be  not  insulated.  On 
forming  a  connection  by  a  conductor  between 
Fi  143  *k°  interior  and  exterior  surfaces,  the  equili- 
brium is  at  once  restored  by  a  rush  of  the  op- 
posing forces,  accompanied  with  a  brilliant  flash  of  artificial 
lightning.  If  the  hand  of  the  operator  is  the  conducting 
medium,  a  violent  shock  is  felt,  commonly  known  as  the 
electrical  shock.  A  series  of  such  jars,  arranged  so  as  to  be 
charged  by  one  machine,  is  called  an  electrical  battery,  as 

shown  in  figure  144,  where  all 
the  inside  coatings  unite,  and 
also  all  the  outsides  are  con- 
nected. The  battery  may  also 
be  so  constructed  as  to  allow  of 
the  jars,  after  they  are  charged, 
being  shifted  so  that  the  series 
shall  be  discharged  consecutive- 
ly,  each  outer  connected  with 
j?-l(r  -^  the  next  inner  coating.  Great 

intensity  is  thus  obtained. 

What  terms  describe  these  conditions?  173.  What  is  the  Leyden 
jar?  What  its  theory  ?  What  is  an  electrical  battery  ? 


112  ELECTRICITY. 

174.  By  using  an  insulated 
jointed  rod,  (fig.  145,)  called  a 
discharging  rod,  the  experimenter 
avoids  receiving  the  shock. 

When  the  shock  of  the  electri- 
cal   battery   is   passed    through 
a  card,  (fig.  146,)  the  hole  which  is 
Fig.  145.        pierced  is  burred  on  both  sides. 
This  fact  has  been  adduced  as  a  proof  that  there 
were  two  fluids,  moving  in  different  directions. 
Otherwise  it  would  seem  that  the  burr  should 
exist  only  on  one  side. 

175.  The  dissected  Leyden  jar  (fig.  147)  is     Fig.  146. 

so  constructed  that  we  may  remove  the  interior 
coating  from  its  glass  jar  &,  leaving  the  outer  coat- 
ing alone.  This  may  be  done  after  the  jar  is 
charged,  when  the  separate  parts  will  not  manifest 
excitement,  as  tested  by  the  electroscope.  When 

reunited,    however,  a   spark   can    still   be   drawn 

Fig.  147.  from  it. 

If  the  Leyden  jar  is  placed  on  an  insu- 
lating stand  s,  (fig.  148,)  it  will  be  found 
impossible  to  charge  it.  The  most  power- 
ful machine  a  will  communicate  only  one  or 
two  eparks  to  it,  6.  This  is  because  the 
negative  excitement  cannot  pass  off  from 
the  outer  coating.  Accordingly,  if  the  ball 
of  a  second  jar  c,  uninsulated,  be  brought 
Fig.  148.  near  the  outer  coating,  a  torrent  of  sparks 
flows  off,  and  both  jars  are  quickly  charged.  Attention  to 
the  laws  of  attraction  and  repulsion  gives  us  an  easy  solu- 
tion of  this  problem,  which  involves  the  whole  theory  of  the 
Leyden  jai\  It  is  also  obvious  that  glass  is  not  an  impedi- 
ment to  the  induction  of  electrical  excitement,  however  per- 
fect it  may  be  as  a  non-conductor. 

176.  Dr.  Faraday  has  shown  that  the  inductive  action  of 
ordinary  electricity  takes  place  in  curves  which  are  analo- 
gous to  the  lines  of  force  surrounding  a  magnet — forming  its 
atmosphere  of  influence,  so  to  speak. 

174.  What  is  a  discharging  rod?  What  does  the  card  experiment 
show?  175.  What  is  the  dissected  jar  ?  Describe  the  experiment  in 
fig.  148.  176.  How  does  electrical  induction  occur?  Name  the  induc- 
tive power  of  glass,  lac,  sulphur,  «fcc. 


ELECTRICITY  OP   FRICTION.  113 

Substances  also  differ  in  their  specific  power  of  inductive 
capacity:  thus,  air  being  unity,  the  inductive  capacity  of  glass 
is  1-76,  of  lac  2,  and  of  sulphur  2-25.  All  gases  also  have 
the  same  inductive  capacity,  however  they  may  differ  in 
density  or  other  respects. 

177.  The  Electropliorus  is  a  convenient  mode  of  obtain- 
ing an  electrical  spark,  when  no 

electrical  machine  is  to  be  had, 
and  consists  of  a  shallow  tray 
of  tin,  the  size  of  a  dining  plate, 
partly  filled  with  melted  shellac 
a,  or  some  other  resinous  pre- 
paration, made  as  smooth  as 
possible.  A  disc  of  brass  &, 
with  a  glass  handle,  is  provided,  and  the  bed  of  resin  is 
rubbed  with  a  dry  flannel  or  cat-skin :  this  excites  negative 
electricity,  and  the  metal  disc  is  then  laid  on  the  excited 
surface,  and  touched  with  the  finger,  which  receives  a  nega- 
tive spark.  A  coating  of  positive  electricity  is  induced  on  b, 
which  may  be  raised,  and  discharged  by  a  conductor,  giving 
a  vivid  spark,  sufficient  to  explode  gases.  The  resinous 
electricity  not  being  conducted  away  from  the  shellac,  the 
spark  may  be  repeated  as  long  as  the  excitement  lasts.  It 
is  plain  that  the  electricity  in  this  case  is  induced  by  the 
excited  lac. 

If  a  mixture  of  red-lead  and  flowers  of  sulphur,  previously 
well  mixed  in  a  mortar,  be  blown  from  a  tube  over  the  ex- 
cited surface  of  the  electrophorus,  the  two  substances  are 
immediately  separated,  because  of  their  opposite  electrical 
relations,  and  are  arranged  in  curious  figures  on  opposite 
sides  of  the  excited  disc. 

178.  A.  jet  of  high  steam,  issuing  from  a  locomotive  or 
other  insulated  steam-boiler,  will,  with  certain  precautions, 
give  a  stream  of  electrical  sparks  more  powerful  than  any 
electrical  machine.     This  has  been  called  hydro-electricity, 
and  is  produced  by  the  friction  of  the  hot  steam  on  the 
edges  of  the  orifice  from  which  the  steam  issues. 

177.  What  is  the  electrophorus?  What  is  its  theory?  How  do*l 
led-lead,  <fcc.  behave  on  it  ?  178.  What  is  hydro-electricity  ? 


114  ELECTRICITY. 


Galvanism,  Voltaism,  or  Electricity  of  Chemical  Action. 

179.  History. — Galvani,  of  Bologna,  in  the  year  1790, 
accidentally  observed  that  the  freshly  denuded  legs  of  a  frog, 
suspended  on  a  metallic  conductor,  were  powerfully  con- 
vulsed when  brought  near  to  an  active  electrical  machine. 
From  this  trivial  observation  has  sprung  one  of  the  most 
wonderful  departments  of   human  knowledge.     The  same 
fact  had  been  previously  noticed,  and  Swammerdam  had 
exhibited  it  before  the  Grand  Duke   of  Tuscany,  but  no 
result  of  value  was  deduced  from  it.     It  was  suggested  that 
there  was  a  peculiar  sensitiveness  to  electrical  excitement 
in  animal  substances,  due  to  some  remaining  vital  energy. 
This   explanation  failed  to   satisfy  Galvani,  who  observed 

similar  convulsions  in  the  frog's  limbs  when 
<b  hanging  from  a  copper  wire  b  (fig.  150)  on 
,an  iron  rail.  He  found  that  the  effects  were 
produced  whenever  the  muscles  touched  the 
iron  while  the  nerves  touched  the  copper,  but 
that  contact  with  the  copper  alone  did  not 
produce  them.  The  crural  nerves  are  easily 
exposed  by  separating  the  large  muscles  with 
the  fingers  at  a  a.  From  his  observations, 
Galvani  inferred  that  there  was  a  peculiar 
variety  of  electricity  in  animals,  which  he 
called  animal  electricity — that  this  was  de- 
veloped whenever  connection  was  made  be- 
Fi  f*  150  tween  the  muscle  and  naked  nerve  by  means 
of  two  metals.  This  theory  fascinated  the 
physiologists,  and  for  ten  years  Galvani's  experiments  were 
repeated  with  great  zeal  in  all  civilized  countries. 

180.  Volta,  of  Pavia,  maintained  that  it  was  the  contact 
of  two  metals  which  generated  the  electricity,  of  which  the 
frog's  legs  were  only  a  delicate  electroscope.     This  experi- 
ment can  never  fail  to  excite  wonder,  however  often  we  may 
perform  it.     We  suspend  from  a  metallic  conductor  a  pair 
of  frog's  legs  recently  skinned,  and  with  a  part  of  the  spine 
attached.    With  two  metallic  slips,  one  of  zinc  and  one  of 
copper,  we  touch  at  the  same  time  the  naked  nerve  and  the 

179.  What  was  Galvani's  observation?     What  was  the   suggestion? 
What   did   Galvani   infer?     How   was   his   animal   electricity  excited 
180.  What  did  Volta  maintain?     What  was  his  observation  with  tho 
frog's  legs  ? 


ELECTRICITY   OF   CHEMICAL   ACTION.  115 

muscle,  as  shown  in  fig.  151.  Convulsions 
iniftiediately  throw  the  limbs  into  the  po- 
sition indicated  by  the  dotted  lines ;  and 
we  may  repeat  the  trial  until,  after  a  time, 
this  power  gradually  dies  out.  In  proof 
of  his  views,  Volta  invented  and  brought 
forward  his  memorable  pile,  of  which  a 
more  particular  mention  will  be  made  Fig- 151. 
presently. 

181.  This  is  not  the  place  to  record  in  detail  the  history 
of  science,  but   this   discovery  is    one    of  the  few   grand 
achievements  of  the  human  mind  which  must  ever  mam 
the  moment  of  a  new  era  in  experimental  philosophy.     It  ia 
both  wonderful  and  instructive  to  reflect  that  so  simple  an 
observation  as  the  twitching  of  a  frog's  legs  should  have  led 
immediately  to  a  revelation  of  the  metallic  basis  of  the  en- 
tire crust  of  our  planet — to  the  adoption  of  a  new  classifica- 
tion of  elements  and  of  their  compounds — to  almost  mi- 
raculous performances  in  metallurgy — and  to  the  instanta- 
neous communication  of  thought,   by  the  annihilation  of 
time  and  space  ! 

182.  Voltaic  Pile. — Volta  sagaciously  reasoned  that  the 
effects  observed  by  Galvani  could  be  produced  with  simple 
metals  and  a  fluid,  or  substances  saturated  with  a  fluid.   The 
truth  of  this  conjecture  is  easily  verified  by  placing  on  the 
tongue  a  silver  coin,  and  beneath  it  a  slip  of  zinc  or  a  cop- 
per coin.     On  touching  the  edges  of  the  two  metals  so 
situated,  we  perceive  a  mild  flash  of  light  and 

a  sharp  prickling  sensation  or  twinge,  giving 
notice  of  the  production  of  a  voltaic  current. 
This  simple  experiment  was  made  long  before 
the  discoveries  of  Galvani  and  Yolta,  and  is 
to  be  regarded  as  the  first  recorded  observation 
in  the  remarkable  science  of  galvanism.  Volta 
accordingly  arranged  a  series  of  copper  and 
silver  coins  in  a  pile,  with  cloths  wet  in  a 
saline  or  acid  fluid  between  them.  The  ar- 
rangement is  seen  in  fig.  152.  The  copper  c 
and  zinc  z  alternate  with  the  wet  cloth  be- 
tween. The  pile  begins  with  z  and  ends  with  c,  and  care 

What  did  be  invent?     181.  What  reflection  is  here  made  ?    182.  What 
was  Volta's  reasoning  ?    What  is  the  simplest  form  of  battery? 


116  ELECTRICITY. 

must  be  taken  that  the  order  be  strictly  maintained,  viz. 
copper — cloth — zinc.  On  establishing  a  metallic  commuai- 
cation  between  these  extremes  (poles)  by  a  wire,  a  current 
of  electricity  flows  in  the  direction  of  the  arrow  on  the  wire. 
If  orie  hand  be  placed  on  each  end  of  the  pile,  a  shock 
will  be  experienced,  similar  in  some  respects  to  that  from 
the  electrical  machine,  and  yet  very  unlike  it.  If  the  pile 
has  many  members,  on  touching  the  wires  communicating 
between  the  extremes  the  shock  is  very  intense,  and  a  vivid 
spark  will  be  produced,  which  is  increased  if  points  of  pre- 
pared charcoal  are  attached  to  the  ends  of  the  wires.  The 
conducting  wires  held  together  will  grow  hot,  and  if  a  short 
piece  of  small  platina  wire  is  interposed,  it  will  be  heated 
to  bright  redness.  Such  is  an  outline  of  the  remarkable 
discovery  of  Volta.  whose  pile  was  made  known  to  the 
world  in  1800.  The  principle  involved  in  this  arrangement 
is  unaltered,  although  more  manageable  and  efficient  forms 
of  apparatus  have  supplied  the  place  of  the  original  pile. 

183.  Simple  Voltaic  Circle. — A  voltaic  current  is  esta- 
blished whenever  we  bring  two  dissimilar  metals  (as  copper, 
silver,  or  platina,  with  zinc  or  iron)  into  contact  in  an  acid 
-* — «c  or  saline  fluid.  Thus,  if  we  place  a  slip  of 
copper  in  a  glass  of  acid  water,  and  beside  it 
in  the  same  vessel  a  slip  of  amalgamated  zinc, 
(fig.  153,)  as  long  as  the  two  metals  do  not 
touch  there  will  be  no  action,  but  on  bringing 
together  the  upper  ends  of  the  two  slips  of 
metal,  a  vigorous  action  will  commence,  bub- 
bles of  gas  will  be  rapidly  given  off  from  the 
Fig.  153.  copper,  while  the  zinc  will  be  gradually  dis- 
solved in  the  acid  water.  This  action  will  be  arrested  at 
any  moment,  on  separating  the  two  metals.  If  this  separa- 
tion is  made  in  the  dark,  a  minute  spark  will  also  be  seen. 
The  action  here  is  entirely  electrical.  The  end  of  the.  zinc 
in  the  acid  is  -{->  or  positive,  and  that  in  the  air  — ,  or  ne- 
gative ;  the  copper  has  the  reverse  signs.  These  relations 
are  expressed  in  the  figures  by  the  signs  -j-  and  — ,  and  by 
the  direction  of  the  arrows  showing  the  -f-  electricity  of  the 
zinc  passing  to  the  —  of  the  copper  in  the  acid;  while  the 
bubbles  of  gas  (hydrogen)  set  free  at  the  -f-  end  of  the  zinc 

Describe  the  pile,  fig.  152.  183.  What  are  the  conditions  of  a  voltaio 
circuit?  How  is  its  action  suspended?  What  are  the  electrical  states  of 
the  immersed  metals  ?  Illustrate  by  figs.  153,  154. 


ELECTRICITY   OF   CHEMICAL   ACTION. 


117 


are  delivered  at  the  —  of  the  copper.  Fig.  154  shows  how 
the  current  may  be  established  by  wires, 
without  the  direct  contact  of  the  slips.  In 
this  case  the  wires  (as  in  the  pile)  carry  the 
influence  in  the  direction  of  the  arrows,  and 
the  existence  of  the  current  and  its  positive 
and  negative  characters  may  be  shown  by 
the  effect  produced  by  it  on  a  small  mag- 
netic needle,  which  will  be  influenced  by 
the  wires  carrying  the  current,  just  as  by 
the  magnet — being  attracted  or  repelled 
according  as  it  is  above  or  below  the  wire, 


Fig.  154. 


and  in  either  case  endeavoring  to  place  itself  at  right  angles 
to  the  conducting  wire,  (201.)  The  direction  of  the  voltaic 
current  (and  of  course  the  -f-  or  —  qualities  of  the  metals 
from  which  it  is  evolved)  depends  entirely  on  the  nature  of 
the  chemical  action  produced.  Thus,  if,  in  the  arrangement 
just  described,  strong  ammonia  were  used  in  place  of  the 
dilute  acid,  all  the  relations  of  the  metals  and  the  fluid 
would  be  reversed,  since  the  action  would  then  be  upon  the 
copper. 

184.  Thus  is  electricity  the  result  of  chemical  action ; 
and  conversely  we  see  that,  under  the  arrangement  described, 
chemical  action  is  controlled  by  the  electrical  condition  of 
the  metals.     This  is  electricity  in  motion,  or  dynamic  elec- 
tricity; and  frictional  electricity  may  be  regarded  as  stag- 
nant or  statical  electricity.     Let  us  attend  somewhat  further 
to  the  theory  of  the  voltaic  circle. 

185.  In  the  compound  voltaic  circuit,  composed  of  two 
or  more  members,  connection  is  formed,  not  between  members 
of  the  same  cell,  but   between    those    of  opposite   names 
in  contiguous  cells. 

This  is  seen  by  in- 
specting the  arrows 
and  signs  -(-  and  — 
in  figure  155.  The 
electricity  always 
flows,  both  in  simple 
and  compound  cir- 
cles, from  the  zinc 
to  the  copper,  in  the 


Fig.  155. 


184.  How  is  this  mode  of  electricity  regarded  ?     185.  What  are  the  con- 
ditions  of  a  compound  voltaic  series  ?     Describe  it  in  fig.  155. 


118  ELECTRICITY. 

fluid  of  the  battery;  and  from  the  copper  to  the  zinc,  out 
of  the  battery.  This  is  important  to  be  remembered,  since 
the  zinc  is  called  the  electro-positive  element  of  the  voltaic 
series,  although  out  of  the  fluid  it  is  negative ;  and  conse- 
quently, in  voltaic  decomposition,  that  element  which  goes 
to  the  zinc-pole  is  called  the  electro-positive  element,  being 
attracted  by  its  opposite  force;  while  the  element  going 
to  the  copper  is  called,  for  the  same  reason,  the  electro- 
negative. The  compound  circle,  reduced  to  the  simplest 
form  of  expression,  would  be — 

Copper — zinc — -fluid — copper — zinc. 
Here  the  copper  end  is  negative  and  the  zinc  positive, 
but  the  two  terminal  plates  are  in  no  way  concerned  in  the 
effect ;  so  that,  throwing  them  out  of  the  question,  we  bring 
it  to  the  state  of  the  simple  circle,  which  is  simply — 

Zinc — -fluid — copper  ; 

and  here  we  find  the  zinc  end  negative,  and  the  copper  end 
positive. 

186.  A  certain  resistance  to  the  passage  of  a  voltaic  cir- 
cuit is  offered  by  every  element  used  in  its  construction. 
New  properties  are  thus  acquired  by  the  compound  circuit, 
which  are  never  seen  in  the  single  couple,  while  the  latter 
possesses  certain  attributes  not  seen  so  well  in  the  compound 
series.     For  example,  no  single  pair  of  plates,  however  large, 
will  afford  a  current  capable  of  decomposing  water  or  of 
affording  an  electrical  shock,  although  a  maximum  of  mag- 
netic effect  may  thus  be  produced.     These  differences  were 
formerly  ascribed,  rather  vaguely,  to  what  has  been  called 
quantify  and    intensity.     Thus,  in   the    compound    circuit, 
supposing  each  -j-  and  —  in  the  circuit  to  neutralize  each 
other,  then  only  the  final  quantities  -j-  and  —  remain  as 
expressed  in  the  poles;  and  it  was  argued  that  the  quantify 
of  electricity  was  no  greater  than  would  be  afforded  by  a 
single  couple,  while  its  intensity,  owing  to  the  resistance  over- 
come in  each  cell,  was  greatly  increased.     This  matter  has 
been  placed  on  the  basis  of  mathematical  demonstration  by 

187.  Ohm's  Law.—Qhrn,   of  Berlin,  in  1827  first  de- 
monstrated that,  as  the  voltaic  apparatus  itself  is  composed 

186.  What  effect  is  due  to  each  element  ?  "What  new  properties  clooa 
the  current  thus  acquire?  What  was  meant  by  quantity  and  intensity  ? 
187.  What  law  expresses  the  conditions  of  a  voltaic  circuit? 


ELECTRICITY   OF   CHEMICAL  ACTION.  119 

solely  of  conductors,  the  electric  current  must  proceed,  not 
only  along  the  connecting  wire,  from  pole  to  pole,  but  also 
through  the  whole  apparatus ;  that  the  resistance  offered  to 
the  passage  of  the  current  consisted  therefore  of  two  parts, 
one  exterior  to,  and  one  within,  the  apparatus.  This  expla- 
nation cleared  up  at  once  the  difficulties  which  had  previously 
beset  this  subject  when  regarded  only  in  view  of  the  exterior 
resistance. 

Let  the  ring  a  b  c  in  fig.  156  represent  a  homo- 
geneous  conductor,  and  let  a  source  of  electricity 
exist  at  A.  From  this  source  the  electricity  will  /  \ 

diffuse  itself  over  both  halves  of  the  ring,  the  I  I 

positive  passing  in  the  direction  a,  the  negative    \^^/ 
in  b,  and  both  fluids  meeting  at  c.     Now  it  fol- 
lows, if  the  ring  is  homogeneous,  that  equal  quan-     Fis<  156* 
tities  of  electricity  pass  through  all  cross  sections  of  the 
ring  in  the  same  time.     Assuming  that  the  passage  of  the 
fluid  from  one  cross  section  of  the  ring  to  another  is  due  to 
the  difference  of  electrical  tension  at  these  points,  and  that 
the  quantity  which  passes  is  proportional  to  this  difference 
of  tension,  the  consequence  is  that  the  two  fluids  proceeding 
from  A  must  decrease  in  tension  the  farther  they  recede 
from  the  starting  point. 

188.  This  decreasing  tension  may  be  represented  by  a 
diagram.  Suppose  the  ring  in  fig.  156  to  be  stretched  out 
to  the  line  A  A'.  Let  the  ordinate 
A  B  represent  the  tension  of  positive 
electricity  at  A,  and  A'  B'  that  of  the 
negative  fluid ;  then  the  line  B  B' 
will  express  the  tension  for  all  parts 
of  the  circuit,  by  the  varying  lengths 
of  A  B,  A'  B'  at  every  point  of  A  c  or 
c  A'.  Hence  Ohm's  celebrated  formula,  F  =  -|,  where  F 
represents  the  strength  of  the  current,  E  the  electro-motive 
force  of  the  battery,  and  B,  the  resistance.  Therefore  the 
greater  the  length  of  the  circuit,  the  less  will  be  the  amount 
of  electricity  which  passes  through  any  cross  section  in  a 
given  time.  In  exact  terms,  this  law  states  that  the  strength 


Demonstrate  fig.  156.  188.  How  do  you  express  the  decreasing  ten . 
»ion  ?  What  is  Ohm's  formula  ?  Give  the  meaning  of  each  expression. 
What  is  the  la^r  as  stated? 


120  ELECTRICITY. 

of  the  current  is  inversely  proportional  to  the  resistance  of  the 
circuit,  and  directly  as  the  electro-motive  force. 

189.  But  in  the  simplest  voltaic  circuit  we  have  not  a 
homogeneous  conductor,  but  several  of  various  powers  in 

this  respect.     To  illustrate  this,  let  the 
conductor  A  A'  (fig.  158)  consist  of 
two   portions   having    different    cross 
sections.     For  example,  let  the  cross 
section  of  A  d  be  n  times  that  of  d  A'  j 
then  if  equal  quantities  pass  through 
all  sections  in  equal  times,  if  through 
a  given  length  of  the  thicker  wire  no  more  fluid  passes  than 
through  the  thinner  wire,  the  difference  of  tension  at  both 
ends  of  this  unit  of  length  of  the  thicker  wire  must  be  only 

-th  of  what  it  is  in  the  latter.  Thus,  "  the  electric  fall,"  as 
Ohm  calls  it,  will  be  less  in  the  case  of  the  thick  wire  than 
of  the  thinner,  as  shown  by  the  line  B  a  in  the  figure.  The 
result  is  expressed  in  the  law  that  the  "electric  fall"  is 
directly  as  the  specific  resistances  of  the  conductors,  and  in- 
versely as  their  cross  sections.  Hence,  the  greater  the  resist- 
ance offered  by  the  conductor,  the  greater  the  fall.  The 
very  simplest  circuit  must  therefore  present  a  series  of  gra- 
dients expressive  of  the  tension  of  its  various  points — as 
one  for  the  connecting  wire,  one  for  the  zinc,  one  for  the 
fluid,  and  one  for  the  copper.  The  electro-motive  force  of 
a  voltaic  couple  ("  E"  of  Ohm's  formula)  may  be  experi- 
mentally determined,  and  it  is  proportional  to  the  electric 
tension  at  the  ends  of  the  newly  broken  circuit. 

190.  Galvanic  Batteries  are  constructed  of  various  forms, 
according  to  the  purpose  for  which  they  are  to  be   used. 

One  of  the  earliest 
forms  contrived  was  the 
Cruickshauk's  trough, 
(tig.  159,)  in  which  the 
plates  of  copper  and 
zinc  soldered  together 
are  secured  in  grooves  by  cement,  water-tight,  all  the  zincs 
facing  in  one  direction.  The  acid  was  poured  into  the 

189.  How  does  it  apply  to  conductors  not  homogeneous  ?  What  is  the 
electric  fall  ?  Give  the  law.  Describe  the  course  of  the  current  in  and 
out  of  the  fluid.  What  is  the  simplest  expression  of  tho  compound 
circle  ?  190.  What  was  Cruickshank's  battery  ? 


ELECTRICITY  OF   CHEMICAL   ACTION.  121 

trough  until  the  cells  were  filled.  To  avoid  the  incon- 
venience arising  from  loss  of  power,  (which  in  this  form  of 
instrument  is  greatest  at  the  first  moment  of  contact  be- 
tween the  plates  and  the  acid,)  Dr.  Hare  contrived  his 
revolving  deflagrators.  These  were  so  constructed,  that  by 
a  quarter  revolution  of  the  trough,  the  acid  could  at  plea- 
sure, and  without  disturbing  the  arrangements  of  the 
operator,  be  thrown  off  or  on  the  plates,  and  the  maximum 
effects  of  this  kind  of  the  battery  be  obtained.  But 
recent  improvements  in  the  construction  of  the  battery  have 
supplied  us  with  several  superior  forms  of  the  instrument, 
suited  to  various  purposes,  and  possessing  the  valuable  qua- 
lity of  constancy  of  action. 

191.  Amalgamation. — In  the  original  form  of  the  gal- 
vanic battery,  made  of  copper  and  of  unamalgamated  zinc, 
there  is  a  great  amount  of  local  action  in  each  cell,  arising 
from  the  impurity  of  the  zinc.     When  the  surface  of  the 
zinc  is  amalgamated  with  mercury,  the  local  action  ceases ; 
and  the  amalgamated  surface,  being  reduced  to  one  uniform 
electrical  condition,  will  remain  for  any  length  of  time  in 
the  acid  fluid  unacted  on,  until  connected  with  the  electro- 
negative element.    All  improved  batteries  are  therefore  now 
constructed  with  amalgamated  zinc.     It  should  be  remarked 
that  the    local  action  in  a  battery  cell,   arising  from  the 
cause  named,  not  only  consumes  the  power  of  that  member, 
but  reduces  the  energy  of  the  whole  series.     In  order  to 
have  a  constant  voltaic  circuit  of  equal  power,  not  only  the 
evils  arising  from  local  action  must  be  avoided,  but  also,  as 
far  as  possible,  the  exhaustion  of  the  fluid  of  excitation. 
Batteries  so  constructed  as  to  meet  these  difficulties  are 
called  sustaining  batteries,  or  constant  batteries.     Some  of 
the  more  important  of  these  we  will  briefly  describe. 

192.  Since 's  Battery  is  formed  of  zinc  and  silver,  and 
needs  but  one  cell,  and  one  fluid  to  excite  it.     The  silver 
plate  (S,  fig.  160)  is  prepared  by  coating  its  surface  with 
platinum,  thrown  down  on  it  by  a  voltaic  current,  in  the 
state  of  fine  division,  which  is  known  as  platinum-black. 
The  object  of  this  is  to  prevent  the  adhesion  of  the  liberated 
hydrogen  to  the  polished  silver.     Any  polished  smooth  sur- 
face of  metal  will  hold  bubbles  of  gas  with  great  obstinacy, 

What  was  Hare's  improvement?    191.  What  is  amalgamation  ?    What 
Us  use  ?    What  is  said  of  local  action  ?     192.  What  is  Smee's  battery  ? 


122 


ELECTRICITY. 


thus  preventing  in  a  measure  the  contact 
between  the  fluid  and  the  plate  by  the  in- 
terposition of  a  film  of  air-bubbles.  Tho 
roughened  surface  produced  from  the  de- 
posit of  platinum-black  entirely  prevents 
this.  The  zinc  plates  z  z  in  this  battery 
arc  well  amalgamated,  and  face  both  sides 
of  the  silver.  The  three  plates  are  held  in 
position  by  a  clamp  at  top  b,  and  the 
interposition  of  a  bar  of  dry  wood  w 
prevents  the  passage  of  a  current  from 
plate  to  plate.  Water,  acidulated  with 
one-seventh  its  bulk  of  oil  of  vitriol,  or, 
for  less  activity,  with  one-sixteenth,  is  the 
exciting  fluid.  The  quantity  of  electricity  excited  in  this 
battery  is  very  great,  but  the  intensity  is  not  so  great  as  in 
those  compound  batteries  to  be  described.  This  battery  is 
perfectly  constant,  does  not  act  until  the  poles  are  joined, 
and,  without  any  attention,  will  maintain  a  uniform  flow  of 
power  for  days  together.  A  plate  of  lead,  well  silvered,  and 
then  coated  with  platinum-black,  will  answer  equally  as 
well,  and  indeed  better  than  a  thin  plate  of  pure  silver 
This  battery  is  recommended  over  every  other  for  the  stu- 


Fig.  160. 


Fig.  161. 

dent,  as  comprising  the  great  requisites  of  cheapness,  ease 
of  management,  and  constancy.  A  form  of  it,  well  calcu- 
lated for  the  student's  laboratory,  is  shown  in  fig.  161, 
which  is  a  porcelain  trough  with  six  cells.  This  battery  is 
the  one  universally  employed  in  electro-metallurgy. 

193.  DanieWs  Constant  Battery. — This  truly  philosophi- 
cal instrument  (fig.  162)  is  made  up  of  an  exterior  circular 


What  are  the  advantages  of  Smce's  battery  ? 


ELECTRICITY    OF    CHEMICAL    ACTION. 


123 


cell  of  copper  C,  three  and  a  half  inches  in  diameter, 
which  serves  both  as  a  containing  vessel  and  as 
a  negative  element ;  a  porous  cylindrical  cup 
of  earthenware  P  (or  the  gullet  of  an  ox  tied 
into  a  bag)  is  placed  within  the  copper  cell, 
and  a  solid  cylinder  of  amalgamated  zinc  Z 
within  the  porous  cup.  The  outer  cell  C  is 
charged  by  a  mixture  of  eight  parts  of  water 
and  one  of  oil  of  vitriol,  saturated  with  blue 
vitriol,  (sulphate  of  copper.)  Some  of  the  solid 
sulphate  is  also  suspended  on  a  perforated  shelf, 
or  in  a  gauze  bag,  to  keep  up  the  saturation. 
The  inner  cell  is  filled  with  the  same  acid 
water,  but  without  the  copper  salt.  Any  num- 
ber of  cells  so  arranged  are  easily  connected 
together  by  binding  screws,  the  C  of  one  pair  -p-  ^ 
to  the  Z  of  the  next,  and  so  on.  This  instru- 
ment, when  arranged  and  charged  as  here  described,  will 
give  out  no  gas.  The  hydrogen  from  the  decomposed  water 
is  not  given  off  in  bubbles  on  the  copper  -side,  as  in  all  forms 
of  the  simple  circuit  of  zinc  and  copper ;  because  the  sulphate 
of  copper  there  present  is  decomposed  by  the  circuit,  atom 
for  atom,  with  the  decomposed  water,  and  the  hydrogen 
takes  the  atom  of  oxyd  of  copper,  appropriating  its  oxygen 
to  form  water  again,  and  metallic  copper  is  deposited  on 
the  outer  cell.  No  action  of  any  sort  results  in  this  battery, 
when  properly  arranged,  until  the  poles  are  joined.  Ten  or 
twelve  such  cells  form  a  very  active,  constant,  and  econo- 
mical battery. 

194.  In  the  common  sulphate  of  copper  battery  (fig.  163) 
only  the  acid  solution  of  sulphate  of  copper  is 

used.     The  surface  of  zinc  becomes  soon  en- 
cumbered by  the  metallic  copper  in  a  state  of 
fine  division  thrown  down  upon  its  surface. 
It  is  a  very  useful   battery  for  electro-mag-       I 
netic  purposes. 

195.  Groves  Battery. — Mr.  Grove,  of  Lon- 
don,  has   contrived   a   compound    sustaining 

battery,  of  great  power  and  most  remarkable  intensity  of 
action.     The  metals  used  are   platinum  and  amalgamated 


193.  What  is  Daniell's  battery  ?     194.  What  is  the  sulphate  of  coppe? 
battery  ?     What  is  Grove's  battery  ? 


124 


ELECTRICITY. 


Fig.  164. 


zinc.  A  vertical  section  of  this  battery  is  shown 
in  fig.  164.  The  platinum  -f-  is  placed  in  a 
porous  cell  of  earthenware,  containing  strong 
nitric  acid.  This  is  surrounded  by  the  amalga- 
mated zinc  —  in  an  outer  vessel  of  dilute  sul- 
phuric acid,  (six  to  ten  parts  water  to  one  of 
acid,  by  measure.)  The  platinum,  being  the 
most  costly  metal,  is  here  surrounded  by  the 
zinc,  in  order  to  economize  its  surface  as  much 
as  possible.  In  this  battery  the  hydrogen  of 
the  decomposed  water  on  the  zinc  side  enters  the 
nitric  acid  cell,  decomposes  an  equivalent  of  the 
acid,  forming  water  with  one  equivalent  of  its 


oxygen,  while  the  deutoxyd  of  nitrogen  is  given  out  as  a 
gas,  and,  coming  in  contact  with  the  air,  is  converted  into 
hyponitric  acid  fumes.  No  other  form  of  battery  can  be  com- 
pared with  this  for  intensity  of  action.  A  scries  of  four 
cells  (the  platinum  foil  being  only  three  inches  long  and 
half  an  inch  wide)  will  decompose  water  with  great  rapidity; 
and  twenty  such  cells  will  evolve  a  very  splendid  arch  of 
light  from  points  of  prepared  charcoal,  and  deflagrate  all 
the  metals  very  powerfully.  It  is  rather  costly,  and  trouble- 
some to  manage,  as  are  all  batteries  with  double  cells  and 
porous  cups. 

196.  Bunscn's  carbon  lattery  is  a  valuable  addition  to  our 
resources  in  this  department.  It  employs  a  cylinder  of  car- 
bon for  the  negative  element,  in  place  of  the 
platinum  in  Grove's  battery.  The  carbon  is 
that  of  the  gas-works,  pulverized  and  mould- 
ed with  flour,  and  afterward  baked  like  pot- 
tery into  compact  cylinders.  This  battery 
(fig.  165)  has  the  advantage  of  large  mem- 
bers and  great  cheapness  of  construction. 
Fifty  large-sized  members,  10  inches  high, 
the  outer  cups  5  inches  in  diameter,  cost 
about  fifty-five  dollars  in  Paris,  made  by  Deleuil,  Rue  du 
Pont-de-Lodi,  No.  8.  The  author  has  found  this,  on  the 
whole,  the  most  efficient  and  economical  of  all  batteries 
suited  to  show  the  more  splendid  and  intense  effects  of 
voltaic  electricity. 


Fig.  165. 


196.  What  is  Bunsen's  battery?     What  is  the  reaction  in  these  com- 
pound  batteries  ? 


ELECTRICITY   OF   CHEMICAL   ACTION. 


125 


197.  The  effects  of  voltaic  electricity  are, 
1.  Physical;  2.  Chemical;  and,  3.  Physio- 
logical.    Under  the  first  head  are  included 
the  electrical,  luminous,  calorific,  and  elec- 
tro-magnetic phenomena  of  the  circuit. 

198.  Deflagration.  —  When  the  current 
from  a  series  of  20  or  50  pairs  of  Grove's 
or   Bunsen's    battery   is    passed   through 
points  of  prepared  charcoal,  as  in  the  dis- 
charger, (fig.  166),  a  most  brilliant  light 
and  intense  heat  are  produced.     No  effect 
is  seen  until  contact  is  made  between  the 
poles  p  and  n,  when,  on  withdrawing  them, 
the  arch  of  light  elongates,  and  connects 
the  separated  poles,  in 

the  manner  shown  in 
fig.  167.  This  arch  is 
in  a  powerful  pile  some 
inches  in  length.  It  is 
accompanied  with  an 
elongation  of  the  pole 
on  the  --  or  carbon 
side  of  the  battery,  and  a  depression  or  hollow- 
ing out  of  the  -J-  or  zinc  side.  This  flame  is 
a  conductor  of  electricity,  and  is  attracted  and 
repelled  by  the  magnet,  as  shown  in  fig.  168. 
By  holding  a  magnet  in  a  certain  position  the 
flame  may  be  made  to  revolve,  accompanied 
at  the  same  time  with  a  loud  sound.  In  the 
small  capsule  of  carbon  S,  (fig.  169,)  gold, 
platinum,  steel,  mercury,  and  other  sub- 
stances are  speedily  fused  and  deflagrated,  with 
various  colored  lights  and  volatilization.  The 
easy  fusion  of  platinum  by  the  pile  is  a  proof  of 
the  intensity  of  the  heat,  as  this  effect  can  be  pro- 
duced by  no  other  source  of  heat  known,  except 
that  of  the  oxyhydrogen  blowpipe.  By  the  union 
of  the  currents  from  several  hundred  carbon  cells, 
M.  Despretz  has  lately  volatilized  the  diamond. 
The  ingenuity  of  the  teacher  will  vary  the  ex- 
periments, always  so  surprising  and  instructive. 


Fig.  166. 


Fis-168 


Fig.  169. 


Fig.  170. 


197.  Classify  the  effects  of  voltaic  electricity. 
of  deflagration.    Which  pole  elongates  ? 


198.  Describe  the  effects 


126 


ELECTRICITY. 


199.  The  electrical  light  of  the  voltaic 
circuit  is  in  no  degree  dependent  on  com- 
bustion, as  may  be  proved  by  establishing 
connection  between  the  poles  in  a  vacuum 
in  a  glass  vessel  exhausted  by  the  air-pump, 
and  containing  the  poles  conveniently  ar- 
ranged, as  in  fig.  170.     No  less  brilliancy 
is  perceived  in  this  case  than  in  the  air. 

200.  A  constant  light  is  produced  from 
the  battery  of  Grove  or  Bunsen,  by  an  in- 
genious   mechanical   arrangement   of  the 
poles.     Fig.  171    shows   that  of   M.  Du- 
boscq,   of   Paris.     The  poles  S  and  I  are 
preserved  at  the  same  distance  by  the  ac- 
tion of  an  electro-magnet  in  the  foot  E, 
upon  a  soft-iron  bar  F  F  in  connection  with 
an  endless  screw  V,  moving  the    pullies 
P  P',  which  are  connected  by  cords  with 
the  poles  S  and  I.     The  contact  of  S  and 
I  induces  magnetism  in  the  electro-magnet 
E,  while  the  springs  R  L  regulate  the  mo- 
tion of  the  machinery.     The  apparatus  is 
simple   and    portable,  and  its  effect  is  to 
make  the  electrical  light  so  steady  and  con- 
stant that  it  may  be  used  for  all  optical  ex- 
periments.    The    author  has   also   shown 
that   good   daguerreotypes  may  be  taken 
with  it  in  a  few  seconds.     For  this  pur- 
pose the  light  is  concentrated  by  a  large 
parabolic  mirror,  so  placed  that  the  poles 
meet  in  its  focus.     The  positive  pole  con- 
sumes much  more  rapidly  than  the  nega- 
tive, both  from  a  more  intense  action  upon 
it  and  because  its  particles  are  carried  over 
and  deposited  on  the  negative  pole,  elon- 
gating the  point  of  the  latter.     To  provide  for  this  difference, 
the  pulley  P'  is  variable,  and  carries  the  pole  I  up  propor- 
tionably  faster,  so  that  the  focal  position  of  the  light  remains 
unchanged. 

How  docs  a  magnet  affect  the  arc  of  flame  ?  199.  How  does  a  vacuum 
affect  the  electrical  light?  Describe  fig.  170.  200.  What  is  the  arrange- 
ment for  rendering  the  light  constant  ?  Describe  fig.  171. 


Fig.  171. 


ELECTRO-MAGNETISM. 

Electro-  Magn  etism. 

201.  Prof.  CErsted,  of  Copenhagen,  in  1819  first  made 
known  the  law  of  electro-magnetic  attraction  and  repulsion. 
If  a  wire  conveying  a  voltaic  current  is  brought  above  and 
parallel  to  a  magnetic  needle,  (as  shown  in  ^ 

fig,  172,)  the  latter  is  invariably  affected, 
as  if  influenced  by  the  poles  of  another 
magnet.     If  the  current  is  flowing,  as  in- 
dicated by  the  arrow  on  the  wire,  say  to 
the   north,    then    the    north  pole    of  the 
needle  will  turn  to  the  east ;  if  the  current 
is  flowing  south,  it  will  turn  to  the  west. 
If  the  wire  carrying  the  current  is  placed 
beneath  the  needle,  the  same  effect  is  produced  as  if  the 
current  had  been  reversed ;  the  needle  turns  in  the  opposite 
way  to  what  it  does  when  the  wire  is  above.     The  effort  of 
the  needle  is  to  place  itself  at  right 
angles  to  the  wire,  as  if  influenced 
by  a  tangential  force.   That  the  wire 
conveying  a  voltaic  current  is  itself 
magnetic,  is  proved  by  this  experi- 
ment.    If  the  wire  is  bent  in  a  rect- 
angle, as  in  fig.  173,  and  wound  with  Fig.  173. 
silk  or  cotton,  to  prevent  metallic  contact,  and  the  lateral 
passage  of  the  power  from  wire  to  wire,  then  it  is  evident 
that  a  current  flowing  over  the  wire  will 
have   to    paiss   many    times    completely 
around  the  needle,  and  the  effect  which 
is  produced  will  be  nearly  in  proportion 
to  the  number  of  turns  made  by  the  wire. 
In  this  way  we  can  make  a  very  feeble 
current  give  decided  indications.     Such 
an  arrangement  is  called  a  galvanoscope 
or  galvanometer. 

202.  In  delicate  galvanoscopes,  in  order   

to  free  the  magnetic  needle  from  the  di-  Fig.  174. 

rective  tendency  which  it  receives  from 

the  earth's  magnetism,  two   needles   are   used,  with  their 
unlike  poles  placed  opposite  to  each  other,  (fig.  174,)  one 

201.  Who  discovered  electro-magnetism  ?    What  effect  has  a  current  on, 
a  wire  ?  What  is  meant  by  a  tangential  force  ?  What  is  a  galvanometer  ? 


128  ELECTRICITY. 

within  and  the  other  above  the  coil.  They  will  then  hang 
suspended  by  the  silk  fibre  which  supports  them,  with  nc 
tendency  to  swing  in  any  direction,  since  they  are  wholly 
occupied  with  their  own  attractions 
and  repulsions,  and  their  directive 
power  is  neutralized.  Consequently, 
they  are  free  to  move  with  the  slight- 
est influence  of  any  current  passing 
through  the  coil.  Such  an  arrange- 
ment is  called  an  astatic  needle.  To 
give  it  greater  delicacy,  and  prevent 
the  currents  of  air  from  moving  it, 
a  glass  shade  (fig.  175)  is  placed  over 
it,  and  the  movements  of  the  needle 
are  read  on  the  graduated  circle.  By 
means  of  a  screw  provided  for  that 
purpose,  the  coil  is  revolved  until  it  is 
Fig  175  parallel  with  the  needle,  as  the  point 

of  greatest  sensitiveness.  The  ten- 
dency of  the  galvanometer  needle,  it  will  be  remembered, 
is  always  to  place  itself  at  right  angles  to  the  direction  of 
the  electrical  current,  that  position  being  the  equator  of  the 
attracting  and  repelling  powers,  and  consequently  a  point 
of  equilibrium. 

203.  Ampere's  Theory. — In  1820,  while  the  original  dis- 
covery of  (Ersted  was  attracting  the  greatest  attention,  M. 
Ampere,  of  Paris,  proposed  to  account  for  the  phenomena 
of  terrestrial  magnetism  by  supposing  a  series  of  electrical 
currents  circulating  about  the  earth  from  east  to  west,  in 
spirals  nearly  at  right  angles  to  its  magnetic  axis.  The 
sun's  rays  impinging  on  the  surface  of  the  earth,  encircle  it, 
so  to  speak,  with  an  unending  series  of  spiral  lines,  pro- 
ducing, by  thermo-electricity,  the  phenomena  of  magnetic  in- 
duction. Arago  found,  in  accordance  with  these  views, 
that  if  iron-filings  were  brought  near  a  connecting  wire 
while  a  voltaic  current  was  passing,  that  they  adhered  to  it 
in  concentric  rings.  These  fell  off  the  moment  the  circuit 
was  broken.  Hence  it  was  inferred  that  if  a  voltaic  current 
was  made  to  pass  in  a  spiral  about  any  conductor,  it  would 
become  magnetic.  This  inference  was  verified  by  the 

202.  What  is  an  astatic  needle  ?  How  is  it  freed  from  the  influence 
of  terrestrial  magnetism?  203.  What  was  Ampere's  theory  ?  What  de- 
monstration did  M.  Arago  devise  ? 


ELECTRO-MAGNETISM. 


129 


Fig.  176. 


204.  Helix. — A  wire  coiled  as  in  fig.  176,  made  the  me- 
dium of  communication  for  a  voltaic  current,  becomes  ca- 
pable of  manifesting  very  strong 

magnetic  influence  on  any  con- 
ductor placed  in  its  axis.  A 
delicate  steel  needle,  laid  in  the 
helix,  will  be  drawn  to  the 
centre  and  held  suspended  there, 
without  material  support,  like 
Mahomet's  fabled  coffin.  If  the  needle  is  of  steel,  the  mag- 
netism it  thus  receives  will  be  retained  by  it ;  but  if  it  be 
of  soft  iron,  it  is  a  magnet  only  while  the  current  is  passing 
Brass,  lead,  copper,  or  any  other  metallic  conductor,  can  by 
galvanism  be  made  to  manifest  temporary  magnetic  power. 
The  polarity  of  the  needle  in  the  helix  will  depend  on  the  di- 
rection in  which  the  current  is  carried;  if  from  right  to  left,  the 
south  pole  will  be  at  the  zinc  end ;  if  from  left  to  right,  this 
polarity  is  reversed.  If  the  spiral  is  reversed  in  the  middle, 
then  a  pair  of  poles  will  be  found  at  the 
point  of  reversal,  and  this  as  often  as  the 
reversal  may  happen.  A  steel  needle  placed 
in  such  a  helix  receives  the  same  reversals. 
Such  an  arrangement  is  shown  in  fig.  177. 

205.  The  polarity  of  the  helix  is  well 
shown  by  the  arrangement  represented  in 
fig.  178,  called  De  la  Rive's  ring.    A  small 
wire  helix,  whose  ends  are  attached  to  the 
little  battery  of  zinc  and  copper  con- 
tained in  a  glass  tube,  floats  on  the 
surface  of  a  basin  of  water,  by  means 

of  a  large  cork,  through  which  the 
glass  tube  is  thrust.  On  exciting 
this  small  battery  by  a  little  dilute 
acid,  poured  into  the  tube,  and 
placing  the  apparatus  on  the  water, 
it  will  at  once  assume  a  polar  direc- 
tion, as  if  it  were  a  compass-needle, 


Fig.  177. 


Fig.  178. 


the  axis  of  the  helix  being  in  the  magnetic  meridian  •  and 
it  will  then  obey  the  influence  of  any  other  magnet  brought 
near  it,  manifesting  the  ordinary  attractions  and  repulsions 

204.  What  is  the  helix?  How  is  a  needle  in  it  affected?  What  po- 
larity has  it  ?  What  does  fig.  177  illustrate  ?  Why  are  the  poles  reversed 
at  N  ?  205.  What  shows  the  polarity  of  the  wire  itself?  Describe  fig.  178. 


130 


ELECTRICITY. 


Fig.  179. 


206.  The  helix  is  placed  as  in  figure 
179,  its  lower  end  dipping  into  a  cup 
of  mercury  p,  in  connection  with  one 
pole  k,  while  it  is  held  by  its  upper 
end  n  in  connection  with  the  other 
pole.  In  this  situation,  when  the  cur- 
rent passes,  the  separate  turns  of  the 
helix  attract  each  other,  thus  shorten- 
ing the  spiral  and  raising  the  point  out 
of  the  mercury,  with  a  vivid  spark. 
This  breaks  the  connection — the  un- 
magnetized  helix  falls — the  point  again 


touches  the  mercury,  when  a  fresh  contraction  happens. 
These  effects  are  made  very  striking  by  holding  one  end  of 
an  iron  rod,  or  of  a  bar  magnet,  within  the  spiral.  If  a 
magnetic  bar  is  used,  the  vibrations  obey  the  ordinary  law 
of  polarity,  ceasing  entirely  when  a  pole  of  like  name  is 
introduced. 

207.  Electro- Magnets. — The  induction  of  magnetism  in 
soft  iron  by  the  voltaic  current,  furnishes  us  the   means 

of  producing  magnets  of  astonishing  power. 
Let  a  b  (fig.  180)  be  a  cylinder  of  soft  iron, 
fitting  the  opening  of  a  helix.  If  the  cur- 
rent from  several  Grove's  batteries  be  passed 
through  the  wires  m  n,  sufficient  magnetic 
power  will  be  developed  to  sustain  a  I,  oscil- 
lating in  a  vertical  line,  even  should  it  weigh 
eight  or  ten  pounds.  This  is  one  of  the  most 
surprising  of  all  experimental  demonstrations. 
By  the  use  of  this  arrangement  on  a  large 
scale,  and  with  a  battery  of  100  members  of  platina,  a  foot 
square,  Dr.  Page  sustained  a  mass  of  soft  iron  600  pounds 
in  weight,  with  a  vertical  movement  of  eighteen  inches. 
On  this  principle  he  has  propelled  a  magnetic  engine  on  a 
railway  at  considerable  speed,  and  sought  to  apply  the  power 
to  other  mechanical  uses. 

208.  Professor  Henry  first  demonstrated  the  fact  that  the 
power  of  an  electro-magnet  with  a   given  voltaic  current 
was  greatly  increased  when  the  helix  wire  was  divided  into 

206.  Explain  the  action  of  the  helix  in  fig.  179.  207.  What  is  an  electro- 
magnet? What  remarkable  result  is  mentioned?  208.  What  did  Pro- 
fessor Henry  iirst  show  ? 


Fig.  180. 


ELECTRO-MAGNETISM. 


131 


coils  of  limited  length.  Availing  himself 
of  this  principle,  he  constructed  electro- 
magnets lifting  over  two  thousand  pounds, 
with  a  single  cylinder  battery  of  small 
size.  All  the  corresponding  ends  of  the 
helices  are  carried  to  their  appropriate 
poles. 

209.  The  ring  helix  (fig.  182)  is  a 
striking  mode  of  exhibiting  the  inducing 
effect  of  a  voltaic  current.  Here  two 
semicircles  of  soft  iron,  fitted  with  han- 
dles, are  magnetized  by  the  current 
passing  in  R,  the  ends  a  b  being  in  con- 
nection with  a  battery.  The  rings  of  iron 
and  of  wire  are  quite  separate,  and,  when 
the  current  passes,  the  iron  (about  f  inch 
diameter)  becomes  so  strongly  magnetic 
as  to  sustain,  easily,  50  pounds.  Small 
electro-magnets  have  been  made  to  sustain 
420  times  their  own  weight. 

210.  Electro-magnetic  Motions. — Faraday 
first  produced  motion  by  the  mutual  action 
of  magnets  and  conductors,  and  Prof.  Hen- 
ry, in  this  country,  about  the  same  time. 
By  various  combinations  of  the  principles 
already  explained,  a  great  number  of  inge- 
nious pieces  of  electro-magnetic  apparatus 
have  been  contrived  for  showing  motion;  by 
wires  attracting  and  repelling — by  circles 
and  rectangles  of  wires  revolving  the  one 
within  the  other — by  armatures  revolving 
before  the  poles  of  permanent  or  electro- 
magnets, and  these  adapted  to  carry  various 
forms  of  machinery.  But  as  these  illus- 
trate no  new  principles,  we  refer  the  student 
to  the  excellent  manual  of  magnetism  by 
Daniel  Davis,  Boston,  where  the  whole 
subject  will  be  found  very  ably  discussed. 
211.  The  Electro-magnetic  Telegraph  is 


Fig.  181. 


Fig.  182. 
a  contrivance 


which  very  happily  illustrates  the  application  of  abstract 


209.  What  does  fig.  182  show?    210.  Who  first  observed  eleetro-i 
netic  motions  ? 


132 


ELECTRICITY. 


scientific  principles  and  discovery  to  the  wants  of  society. 
The  inconceivably  rapid  passage  of  an  electrical  current  ove! 
a  metallic  conductor  was  discovered  by  Watson  in  1747/and 
thi^  discovery  gave  the  first  hint  of  the  possibility  of  using 
electricity  as  a  means  of  telegraphic  communication.  Nume- 
rous attempts  were  made,  very  early  after  this  discovery,  to 
construct  a  telegraph  to  be  worked  by  ordinary  electricity ;  but 
from  difficulties  inherent  in  the  mode,  these  attempts  were 
attended  with  only  very  partial  success.  The  discovery  of 
electro-magnetism  by  GErsted,  in  1820,  supplied  the  neces- 
sary means  of  successful  construction.  Superior  to  all  other 
contrivances  in  the  essential  conditions  of  simplicity,  in  con- 
struction and  notation,  is  the  beautiful  contrivance  patented  by 
Professor  Morse  in  1837.  In  the  accompanying  figure  (183) 


Fig.  183. 

we  have  a  view  of  the  most  essential  parts  of  Morse's  tele- 
graphic register.  A  simple  electro-magnet  m  m,  with  its 
poles  upward,  receives  its  induced  magnetism  from  a  cur- 
rent of  electricity  conducted  by  the  wires  W  W  from  the 
distant  station.  As  soon  as  the  circuit  is  completed,  m  m 
becomes  a  magnet,  and  draws  to  its  poles  an  armature  or  bar 
of  soft  iron  a  on  the  lever  I.  The  motion  of  this  lever  starts 
a  spring  which  sets  in  motion  the  clock  arrangement  c.  This 
clock  machinery,  in  consequence  of  the  weight  attached  to 

211.  Explain  the  principles  of  the  electro-magnetic  telegraph  and  its 

operations. 


ELECTRO-MAGNETISM.  133 

It,  will,  when  once  set  in  motion,  continue  to  move.  The 
immediate  object  of  the  clock  machinery  is  to  draw  forward 
a  narrow  ribbon  of  paper  p  p  in  the  direction  of  the  arrows, 
and  to  cause  it  to  advance  with  a  regular  motion.  The  paper 
ribbon  passes  by  the  end  of  the  pen-lever  ?,  in  which  is  a 
steel  point  s,  that  indents  the  paper  whenever  this  end  of 
the  lever  is  thrown  upward  by  the  attraction  of  the  armature 
a  to  the  magnet  m.  If  m  m  were  constantly  magnetized, 
the  mark  made  by  the  point  s  would  be  a  continuous  line. 
But  we  can  make  and  discharge  an  electro-magnet  as  often 
and  as  fast  as  we  please ;  the  instant,  therefore,  the  circuit 
W  W  is  broken,  m  m  ceases  to  be  a  magnet,  and  lets  go  the 
iron  armature  a,  when  the  point  s  of  the  lever  falls,  so  as 
no  longer  to  mark  the  paper.  The  circuit  being  renewed, 
the  point  marks  again ;  and  this  may  be  repeated  as  often 
as  the  operator  pleases.  The  length  of  time  that  the  circuit 
is  closed  will  be  exactly  registered  in  the  corresponding 
length  of  the  mark  made  by  s.  The  completing  of  the  cir- 
cuit is  performed  by  touching  a  spring  on  the  operator's 
table,  which  establishes  a  metallic  communication  between 
the  poles  of  the  battery.  A  touch  will  produce  a  dot,  a  con- 
tinued pressure  a  long  line,  and  intermitting  repeated  touches 
a  series  of  dots  and  short  lines.  These  easily  form  an  alpha- 
bet. To  complete  the  arrangement,  each  operator  must  have 
his  own  battery  in  connection  with  the  register  at  the  dis- 
tant station.  In  practice,  only  one  wire  is  used  with  each 
register,  the  circuit  being  completed  by  connecting  the  other 
pole  of  the  battery  with  the  moist  earth  by  means  of  a  buried 
metallic  plate  and  a  wire.  The  remarkable  observation  that 
the  earth  could  be  used  in  this  manner  as  a  part  of  the  cir- 
cuit, was  made  by  Steinheil,  in  G-ermany,  in  1837.  Such  is 
a  brief  account  of  one  of  the  most  remarkable  discoveries  of 
modern  times.  In  Bain's  telegraph,  the  circuit  decomposes 
a  salt  of  iron,  staining  a  paper  with  the  marks  of  the  con- 
ductor, and  no  magnet  is  employed. 

212.  The  telegraph  has  become  an  important  auxiliary  in 
astronomical  observations,  by  furnishing  an  exact  means  of 
determining  longitudes.  For  this  purpose  the  principal 
astronomical  observatories  in  the  United  States  are  connected 
by  telegraphic  wires,  and  such  is  the  velocity  of  the  electrical 
wave  that  any  communication  made  from  one  station  will  bo 

212.  How  is  the  telegraph  auxiliary  to  astronomy? 


134  ELECTRICITY. 

received  at  all  the  others  at  almost  the  same  instant.  The 
velocity  of  the  wave  has  been  determined  by  the  experiments 
of  the  Coast  Survey  to  be  about  15,000  miles  in  a  minute. 
Wheatstone  asserts  that  the  wave  of  electricity  moves  as 
rapidly  at  least  as  that  of  light.  Other  very  ingenious  and 
important  applications  have  been  made  of  the  telegraph  for 
regulating  time-pieces  and  for  signalizing  fires.  The  city 
of  Boston  is  provided  with  such  a  system,  a  detailed  descrip- 
tion of  which  may  be  found  in  the  American  Journal  of 
Science  for  January,  1852. 

One  curious  fact  connected  with  the  operation  of  the  tele- 
graph is  the  induction  of  atmospheric  electricity  upon  the 
wires  to  such  an  extent  as  often  to  cause  the  machines  at  the 
several  stations  to  record  the  approach  of  a  thunder-storm. 
This  induction  occasions  a  serious  inconvenience  in  working 
the  telegraph,  not  unattended  with  danger  to  the  operators. 
213.  Professor  Henry  observed  that  when  the  current 
from  a  single  pair  of  plates  was  passed  through  a  long  con- 
ducting wire,  a  vivid  spark  appeared  at  the  instant  of 
breaking  contact  between  the  conductor  and  the  battery ; 
accompanied,  also,  by  a  feeble  shock.  A  long  conductor, 
then,  supplies  the  place  of;  an  increased  number  of  plates  in 
a  voltaic  scries,  and  to  some  degree  imparts  the  quality  of 
intensity  to  a  current  of  quantity.  A  flat  spiral  of  copper 
ribbon,  one  hundred  feet  long,  wound  with  cotton,  and  var- 
nished, shows  these  effects  well. 
The  magnetic  needle  indicates  the 
direction  of  the  current,  (fig.  184.) 
The  opposite  sides  of  the  spiral  of 
course  produce  opposite  effects  on 
the  needle.  The  magnetism  pro- 
duced is,  however,  to  be  distin- 
guished from  the  new  effects  ex- 
cited by  the  passage  of  the  feeble 
Fig  184  current  through  the  coiled  con- 

ductor, on  breaking  contact,  i.  e. 
the  vivid  spark  and  the  shock.  The  latter  is  feeble  with 
100  feet  of  copper  ribbon,  and  becomes  more  intense  if  the 
length  of  the  conductor  be  increased,  the  battery  remaining 
the  same ;  but  the  sparks  are  diminished  by  lengthening 

What  other  facts  are  mentioned  regarding  the  telegraph  ?    213.  What 
was  Henry's  observation  on  the  spiral  ? 


ELECTRO-MAGNETISM.  135 

the  conductor  beyond  a  certain  point.  The  increase  of  in- 
tensity in  the  shock  is  also  limited  by  the  increased  resistance 
or  diminished  conduction  of  the  wire,  which  finally  counter- 
acts the  influence  of  the  increasing  length  of  the  current. 
On  the  other  hand,  if  the  battery  power  be  increased,  the 
coil  remaining  the  same,  these  actions  diminish. 

214.  These  effects  Prof.  Henry  ascribed  to  the  generation 
of  a  secondary  current  at  the  moment  of  breaking  contact. 
This  secondary  current  moves  in  a  direction  opposite  to  that 
of  the  battery  current.  If  a  long  coil  of  fine,  insulated  wire 
be  brought  within  a  small  distance  of  the  flat  spiral,  this 
new  current  will  be  detected  in  the  second  coil.  The  ar- 
rangement used  by  Prof.  Henry  is  seen  in  the  annexed  figure. 
A  small  battery  L  is  connected  with  the  flat  spiral  of  copper 
ribbon  A  by  wires  from  the  battery  cups  Z  and  C.  This 
communication  is  broken  at  will,  by  drawing  the  end  of  one 
of  the  battery  wires  Z  over  the  rasp.  When  the  coil  of  fine 
wire  W  is  in  the  position  indicated  in  fig.  185,  and  the  hands 


Fig.  185. 

grasp  the  conductors,  a  violent  shock  is  felt  as  often  as  the 
circuit  is  broken  by  the  passage  of  the  wire  over  the  rasp. 
When  the  coil  W  contains  several  thousand  feet  of  wiro,  and 
is  brought  near  A,  the  shocks  are  too  intense  to  be  borne. 
As  this  induction  takes  place  through  a  distance  of  many 
inches,  we  can,  by  placing  the  spiral  A  against  a  division 
wall,  or  the  door  of  a  room,  give  shocks  to  a  person  in 
another  room,  who  grasps  the  conductors  of  the  wire  coil  W, 
and  brings  it  near  to  the  wall  on  the  side  opposite  to  A.  A 
screen  or  disc  of  metal  introduced  between  the  two  coils  will 
cut  off  this  inductive  influence.  But  if  it  be  slit  by  a  cut 

214.  What  were  these  currents  called  ?    How  do  they  move  ?    What 
cf  the  spark  and  shock  ? 


136  ELECTRICITY. 

from  the  centre  to  the  circumference,  as  a  & 
in  fig.  186,  the  induction  of  an  intense  current 
in  W  is  the  same  as  if  no  screen  were  present. 
Fig.  186.      Discs  or  screens  of  wood,  glass,  paper,  or  other 
non-conductors,  offer  no  impediment  to  this  induction. 

215.  Induced  Currents  of  the  third,  fourth,  and  fifth  order. 
— If  the  wires  from  W  be  connected  with  another  flat  spiral, 
and  it  with  a  second  coil  of  fine  wire,  and  so  on,  (fig.  187,) 
a  series  of  currents  will  be  induced  in  each  alternation  of 
coils.  The  secondary  intense  current  in  B  will  induce  a 
quantity  current  in  the  second  flat  spiral  C ;  and  a  second 
fine  wire  coil  W  will  induce  a  tertiary  intense  current,  and 
so  on.  These  currents  have  been  carried  to  the  ninth  order, 


decreasing  each  time  in  energy  by  every  removal  from  the 
original  battery  current.  The  polarity,  or  direction  of  these 
secondary  currents,  alternates,  commencing  with  the  second- 
ary. Thus  the  current  of  the  battery  is  -}- ;  and  the  secondary 
current  is  -}- ;  the  current  of  the  third  order  is  — ;  the  cur- 
reut  of  the  fourth  order  is  -j- ;  and  the  current  of  the  fifth 
order  is  — .  These  alternations  are  marked  in  the  figure 
above,  and  were  also  determined  by  Prof.  Henry. 

216.  Compound  Electro-magnetic  Machine. — By  combin- 
ing the  results  just  briefly  enumerated,  a  great  number  of 
ingenious  electro-magnetic  machines  have  been  produced, 
adapted  to  medical  use,  and  illustrative  of  the  induction  of 
magnetism  and  secondary  currents.  One  of  these,  contrived 
by  Dr.  Page,  is  seen  in  fig.  188.  In  this  little  machine,  a 
short  coil  of  stout  insulated  copper  wire  forms  a  helix,  within 
which  some  straight  soft-iron  wires  M  are  placed.  The 

215.  To  what  degree  have  they  been  carried  ? 


ELECTttO-MAflNETTRM.  137 

battery  current  is 
made  to  pass  through 
this  stout  wire,  by 
which  means  mag- 
netism is  induced  in 
the  soft  iron.  The 
conducting  wires  are 
so  arranged  beneath 
the  board  that  the 
glass  cup  C  contain- 
ing some  mercury  is 
in  connection  with  the  battery.  The  bent  wire  W  dips  into 
this  mercury,  and  also  by  a  branch  into  B,  and  when  in  the 
position  shown  in  the  figure,  the  current  from  the  battery 
will  flow  uninterruptedly.  As  soon,  however,  as  the  battery 
connection  is  completed,  M  becomes  strongly  magnetic,  and 
draws  to  itself  a  small  ball  of  iron  on  the  end  of  P;  this 
moves  the  whole  wire  P  W  and  raises  the  point  out  of  the 
mercury  C;  as  the  wire  leaves  the  mercury,  a  brilliant 
spark  is  seen  on  its  surface,  the  contact  being  thus  broken 
with  the  battery,  M  ceases  to  receive  induced  magnetism, 
and  the  ball  P  being  consequently  no  longer  attracted  to 
M,  the  wire  W  falls  by  its  gravity  to  the  position  in  the 
figure.  This  again  establishes  the  battery  connection,  and 
the  same  effects  just  described  recur;  thus  the  bent  wire  W 
receives  a  vibratory  motion,  and  at  each  vibration  a  brilliant 
spark  is  seen  at  C,  and  M  becomes  magnetic.  It  remains 
only  to  mention  that  the  short  quantity  wire  is  surrounded 
by  a  fine  intensity  wire,  2000  to  3000  feet  long,  having  no 
metallic  connection  with  the  battery  or  quantity  wire,  with 
its  ends  terminating  in  two  binding  screws  on  the  left  of 
the  board,  The  fine  wire  receives  a  secondary  induced  cur- 
rent like  the  coil  W,  (185,)  which,  if  touched,  produces  the 
most  intense  shocks  at  each  vibration  of  the  wire.  These 
shocks  are  graduated  by  withdrawing  part  or  all  of  the  soft- 
iron  wires  M. 

217.  Magneto-Electricity. — As  we  have  seen  effects  pro- 
duced from  galvanism  which  exactly  resemble  those  of  ordi- 
nary machine  electricity  and  the  magnetic  influence,  so, 
conversely,  we  might  expect  the  production  of  electrical 
effects  from  the  magnet.  The  electrical  current  from  a  single 

216.  Explain  the  apparatus,  fig.  188. 


138 


ELECTRICITY 


galvanic  pair,  we  have  seen,  produces  magnetism  in  a  spiral 
wire  at  right  angles  with  its  own  course ;  so  the  induction 
of  magnetism  in  soft  iron  from  a  permanent  magnet,  in  like 
manner,  produces  an  electrical  current  at  right  angles  to 
itself  in  the  wire  coiled  on  the  armature.  This  class  of 
phenomena  was  discovered  by  Faraday  in  1831,  and  our 
countryman,  Mr.  J.  Saxton,  soon  contrived  a  machine  very 
similar  to  the  one  in  fig.  189,  called  a  magneto-electrical 


Fig.  189. 

machine.  This  consists  of  a  powerful  magnet  S,  secured  to 
a  board,  with  its  poles  so  situated  that  an  armature,  formed 
of  two  large  bundles  of  insulated  copper  wire  W,  wound  on 
soft-iron  axes,  may  be  revolved  on  an  axis  before  its  poles, 
by  the  multiplying  wheel  M.  A  current  of  electricity  is 
thus  induced  in  W,  just  as  in  the  flat  coils,  the  permanent 
magnet  here  taking  the  place  of  the  flat  spiral.  The  cur- 
rent excited  in  "W  is  led  off  by  conductors  to  the  binding 
screws  p  and  n,  the  continuity  of  the  current  being  broken 
(in  imitation  of  the  rasp  in  185)  by  a  contrivance 
at  6  on  the  axis,  called  a  break-piece,  (fig.  190,) 
which  is  made  by  alternate  ribs  of  metal  c  and 
ivory  i,  the  current  is  broken  by  the  ivory  and 
Fig.  190.  renewed  by  the  metal,  and  at  every  break,  the 
person  whose  hands  grasp  the  conductors,  secured  to  p 
and  n,  feels  a  sharp  shock,  which  may  be  graduated  at 
will  by  the  rapidity  of  the  revolutions  of  M,  and  by  the 
adjustment  of  the  break  b.  A  long  and  fine  wire — say 


217.  What  is  magneto-electricity  ?    Explain  fig.  189. 


THERMO-ELECTRICITY. 


139 


3000  feet  of  wire  -^  of  an  :;_h  in  diameter — is  required 
to  produce  shocks  and  chemical  decompositions.  A  shorter 
and  stouter  wire,  as  250  feet  of  wire  y1^  or  £0  inch  in  dia- 
meter will  produce  no  shock,  but  will  deflagrate  the  metals 
powerfully,  and  produce  a  secondary  current  of  induction 
in  soft  iron.  We  thus  imitate  in  magnetism  the  effects 
produced  from  a  voltaic  current,  the  short  and  stout 
wire  of  the  armature  is  the  simple  circuit  of  large  plates; 
the  long  and  fine  wire  is  like  the  compound  circuit  of  smaller 
plates. 

Thermo-Electricity,  or  the  Electrical  Current  excited 
ly  Heat. 

218.  If  two  metals  unlike  in  crystalline  structure  and 
conducting  power  are  united  by  solder,  and  the  point  of 
their  union  is  heated  or  cooled,  an  electrical 

current  will  be  excited,  which  will  flow  from 
the  heated  point  to  the  metal  which  is  the 
poorer  conductor.    Bismuth  and  antimony  are 
such  metals,  being  bad  conductors,  and  unlike 
in  crystalline  structure.     If  two  bars  of  these 
metals  are  united,  as  in  fig.  191,  and  the  point 
c  is  warmed  by  a  lamp,  a  current  will  be  set       Fig.  191. 
in  motion,  which  will  flow  from  b  to  a,  as  in  the  figure. 
The   compass-needle   may   be    thus 
affected,   as  by  the  voltaic  current. 
For  this  purpose  two  bars  may  be 
mounted  as  in  tig.  192,  and   their 
junction   being  heated   by  a  lamp, 
the    needle    will    swing,   in    conse- 
quence   of    the    electrical    current 
excited  by  the  heat.     When  several  Fig.  192. 

such  are  joined,  we  have  a  greatly  increased 
effect,  as  in  the  thermo-electric  pile  in  Melloni's 
apparatus,  (fig.  193.) 

219.  Thermo-electric  effects  are  not  confined 

to  metals,  for  they  may  be  produced  from  other     Flg' 193> 
solids,  and  even  from  fluids ;  and  a  single  metal,  as  an  iron 
wire,  which  has  been  twisted  or  bent  abruptly,  will  originate 
a  thermo-electric  current  when  the  distorted  part  is  greatly 


218.  What  is  thermo-electricity  ?    How  does  the  current  move  ? 


140 


ELECTRICITY. 


heated.  The  rank  of  the  p*ri)cipal  metals  in  the  thermo- 
electric series  is  as  follows,  beginning  with  the  positive : — 
Bismuth,  mercury,  platinum,  tin,  lead,  gold,  silver,  zinc, 
iron,  antimony.  When  the  junction  of  any  pair  of  these  ia 
heated,  the  current  passes  from  that  which  is  highest  to  that 
which  is  lowest  in  the  list,  the  extremes  affording  the  most 
powerful  combination. 

If  we  pass  a  feeble  current  of  electricity  through  a  pair 
of  antimony  and  bismuth,  the  temperature  of  the  system 
rises,  if  the  current  passes  from  the  former  to  the  latter ; 
but  if  from  the  bismuth  to  the  antimony,  cold  is  produced 
in  the  compound  bar.  If  the  reduction  of  temperature  is 
slightly  aided  artificially,  water  contained  in  a  cavity  in  one 
of  the  bars  may  be  frozen.  Thus  we  see  that  as  change  of 
temperature  disturbs  the  electrical  equilibrium,  so  conversely 
the  disturbance  of  the  latter  produces  the  former. 


Animal  Electricity. 

220.  The  existence  of  free  electricity  in  the  animal  body 
is  proved  by  the  results  of  Aldiui  and  Matteucci.     In  some 

animals  we  see  a  special  apparatus 
for  the  purpose  of  exciting  at  will 
intense  currents  of  electricity. 
There  are  also  such  currents  in  all 
animals.  For  example,  when  the 
lumbar  nerves  of  a  frog,  held  in 
the  manner  shown  in  fig.  194,  are 
touched  to  the  tongue  of  an  ox 
lately  killed,  and  at  the  same  in- 
stant the  operator  grasps  with  the 
other  hand,  well  wetted  in  salt 
water,  an  ear  of  the  ox,  a  con- 
vulsion of  the  frog's  legs  indicates 
Fig.  194.  the  passage  of  an  electric  current. 

221.  The  same  delicate  electroscope  also  shows  similar 
excitement  when  its  pendulous  ischiatic  nerves  touch  the 
human  tongue,  the  toe  of  the  frog  being  held  between  the 


219.  What  range  have  these  effects  ?  How  is  a  fall  of  temperature  ob- 
served in  a  compound  bar  of  antimony  and  bismuth  ?  220.  What  is 
animal  electricity?  Explain  the  experiment  in  iig.  194.  221.  How  else 
is  the  same  fact  shown  ?  How  does  the  cunoat  circulate  ? 


ANIMAL   ELECTRICITY.  141 

moistoned  thumb  and  finger  of  the  experimenter.  This  is 
what  Donne"  calls  the  musculo-cutaneous  current;  passing 
from  the  external,  or  cutaneous,  to  the  internal,  or  mucous, 
covering  of  the  body.  This  current  may  be  de- 
tected, as  was  shown  by  Aldini,  in  the  frog's 
legs  above.  For  this  purpose  he  prepared  the 
lower  extremities  of  a  vigorous  frog,  (fig.  195,) 
and,  by  bending  up  the  leg,  brought  the  muscles 
of  the  thigh  in  contact  with  the  lumbar  nerves  : 
contractions  immediately  ensued.  Thus  it  ap- 
pears from  experiments  made  by  Matteucci,  that 
a  current  of  positive  electricity  is  always  circu- 
lating from  the  interior  to  the  exterior  of  a 
muscle,  and  that  although  the  quantity  is  ex-  g>  95' 
ceedingly  small,  yet  by  arranging  a  series  of  muscles,  having 
their  exterior  and  interior  surfaces  alternately  connected, 
he  produced  sufficient  elec-  (  ^ — £  ~~~\ 

tricity     to     cause     decided          I — • — 4-\ 

effects.     By  a  series  of  half 

thighs  of  frogs,  arranged  as    ^  «nnWm 

in  fig.  196,  he  decomposed  Fig.  196. 

the  iodid  of  potassium,  deflected  a  galvanometer  needle  to 
90°,  and  by  a  condenser  caused  the  gold-leaves  of  au  elec- 
troscope to  diverge.  The  irritable  muscles  of  the 
frog's  legs  form  an  electroscope  56,000  times  more 
delicate  than  the  most  delicate  gold-leaf  electro- 
meter. Professor  Matteucci's  frog-gal  van  oscope 
(fig.  197)  is  therefore  far  the  most  sensitive  test 
of  electricity  that  can  be  employed.  When  the 
pendulous  nerve  is  touched  simultaneously  in  the 
places  where  electrical  excitement  is  suspected, 
the  muscles  in  the  tube  are  instantly  convulsed. 

222.  The  electrical  eel  of  South  America  men- 
tioned by  Humboldt,  and  the  torpedo — a  flat  fish 
found  on  our  own  coast — are  remarkable  examples       Ig'     7' 
of  those  animals  having  a  special  electrical  apparatus  of 
nervous  matter  and  cellular  tissue  arranged  in  the  manner 
of  the  pile.     The  student  is  referred  to  the  lectures  of  Pro- 


What  has  Donne  called  it  ?  How  is  it  shown  in  the  legs  of  the  frog 
alone  ?  How  does  this  current  circulate  ?  How  does  fig.  196  prove  it  ? 
What  is  the  delicacy  of  the  frog-galvan oscope  ?  222.  What  animals  have 
a  special  electric  apparatus  ? 


142 


ELECTRICITY. 


fessor  Matteucci  on  living  beings  for  further  details  on  this 
very  interesting  subject.  We  can  only  add,  that  the  shock 
from  these  animals  is  sufficient  to  charge  a  Ley  den  jar,  to 
produce  chemical  decompositions,  and  to  paralyze  vigorous 
animals. 

The   legs   of  the  common   grasshopper  are,  it  is   said, 
equally  sensitive  electroscopes  as  those  of  the  frog. 


Electro-  Chemical  Decomposition. 

223.  By  far  the   most  interesting   chemical   result    of 
Volta's  pile  was  the  new  power  it  placed  in  the  hands  of 
chemists,  of  unfolding  the  secrets  of  combination,  and  of 
assigning  their  relative  positions  to  the  several  elements. 
Indeed,  the  electro-chemical  theory  has  been  carried  so  far 
by  some  chemists,  that  every  chemical  decomposition  has 
been  referred  to  the  play  of  electrical  forces. 

224.  The  decomposition  of  water  is  the  finest  possible 
illustration  of  this  power.     Water  is  a  compound  of  oxygen 
and  hydrogen  gases,  in  the  proportions  of  one  measure  of 
the  former  to  two  of  the  latter.    When  two  gold  or  platinum 
wires  are  connected  with  the  opposite  ends  of  the  battery, 

and  held  a  short  distance  asunder  in  a  cup 
of  water,  a  train  of  gas-bubbles  will  be  seen 
rising  from  each  and  escaping  at  the  surface. 
With  two  glass  tubes  placed  over  the  plati- 
num poles,  (fig.  198,)  we  can  collect  these 
bubbles  as  they  rise,  and  shall  soon  find  that 
the  gas  given  off  from  the  —  plate  is  twice 
the  volume  of  that  obtained  from  the  -f- 
plate.  When  the  tubes  are  of  the  same  size, 
this  difference  of  volume  becomes  at  once  evi- 
dent to  the  eye.  By  examining  these  gases, 
we  shall  find  them,  respectively,  pure  hydro- 
Fig.  198.  gen  and  pure  oxygen,  in  the  exact  proportion 
of  two  volumes  of  the  former  to  one  of  the  latter.  The 
rapidity  of  the  decomposition  is  greater  when  the  water 
is  made  a  better  conductor,  by  adding  a  few  drops  of 
sulphuric  acid. 


223.  What  was  the  most  interesting  result  of  Volta's  pile  ?     224.  Hovf 
is  water  decomposed  by  it  ?     Describe  fig.  198. 


ELECTRO-CHEMICAL   DECOMPOSITION. 


143 


If  we  employ  a  decomposing  cell  with 
only  one  tube  over  the  conductors,  it  will 
be  found  that  the  gaseous  contents  will 
explode  by  the  electric  spark  or  by  a 
lighted  taper ;  and  if  this  is  done  over 
water  the  perfection  of  the  vacuum  re- 
sulting from  the  explosion  will  be  seen 
by  the  height  of  the  column  which  rises 
in  the  tube,  (fig.  199.) 

225.  We  learn  from  this  most  in- 
structive experiment,  that  the  voltaic 
current  has  power  to  decompose  chemi- 
cal compounds,  that  this  decomposition 
takes  place  in  definite  proportions  of  ^ 
the  constituents — and  that  these  consti- 
tuents  appear   invariably   at    opposite 

poles  of  the  battery.  Fig- 199. 

226.  A  decomposing  cell  interposed  in  the  circuit  will 
give  us  an  exact  account  of  the  amount 

of  electricity  flowing.  Such  an  in- 
strument has  been  called  by  Faraday 
a  voltameter,  (fig.  200.)  It  differs 
from  the  common  decomposing  cell, 
in  having  a  ground-glass  tube  at  top 
bent  twice,  so  as  to  deliver  the  accu- 
mulating gases  into  a  graduated  air- 
vessel,  in  which  their  volume  is  mea- 
sured. A  more  simple  form  of  the 
apparatus  is  easily  constructed,  as  in 
figure  201,  (page  144,)  of  two  glass  Fig.  200. 

tubes,  two  corks,  and  the  conductors  p  p. 

227.  The   experimental   researches   in  electricity   by  Dr. 
Faraday,    which    are   the    basis    of    modern   science    on 
this   subject,    required   the   introduction    of    certain    new 
terms,  some   of  which    require    explanation.     Tho  termi- 
nal wires   or   conductors   of   a   battery  are    often   termed 
the  poles,  as  if  they   possessed  some  attractive  power  by 
which  they  draw  bodies  to  themselves,  as  a  magnet  attracts 
iron.      Faraday  has  shown  that  this  notion  is  a  mistake, 
and  that  the  terminal  wires  act  merely  as  a  path  or  door 

225.  What  does  this  experiment  teach?  226.  What  other  cells  are 
named  ?  227.  What  is  said  of  Faraday's  researches  ?  What  did  they  re- 
quire?  Wrhat  does  he  call  the  poles,  and  why? 


144 


ELECTRICITY. 


PO 

Fig.  201. 


TO  to  the  currents,  and  he  therefore  calls  them 

electrodes,  from  electron  and  odos,  a  way. 
The  electrodes  are  any  surfaces  which  convey 
an  electric  current  into  and  out  of  a  decom- 
posable liquid.  The  term  electrolysis,  from 
electron,  and  the  Greek  verb  luo,  to  unloose, 
is  used  to  express  decomposition ;  and  the 
substances  suffering  decomposition  are  termed 
electrolytes.  Thus,  the  experiment  mentioned 
in  the  last  section  is  a  case  of  electrolysis,  in 
which  water  is  the  electrolyte.  The  elements 
of  an  electrolyte  are  called  ions,  from  the 
Greek  particle  ion,  going,  since  the  elements 
go  to  the  -j-  or  —  electrode.  The  electrodes  are 
distinguished  as  the  anode  and  the  cathode, 
from  ana,  upward,  and  odos,  way,  or  the  way 
in  which  the  sun  rises;  and  kata,  downward, 
and  odos,  or  the  way  in  which  the  sun  sets  '} 
the  anode  is  -f->  and  the  cathode  — .  We  will  now  briefly 
consider  the 

228.  Conditions  of  Electro- Chemical  Decomposition. — 
(1.)  All  compounds  are  not  electrolytes,  that  is,  they  are 
not  directly  decomposable  by  the  voltaic  current.  Many 
bodies,  however,  not  themselves  electrolytes,  are  decomposed 
by  a  secondary  action.  Thus,  nitric  acid  is  decomposed  in 
the  electrical  circuit  by  the  secondary  action  of  the  nas- 
cent hydrogen,  which,  uniting  with  one  equivalent  of  the 
oxygen,  again  forms  water  and  nitrous  acid.  Sulphuric 
acid  is  not  an  electrolyte,  while  hydrochloric  acid  is ;  and 
the  nascent  chlorine  from  the  latter  attacks  the  -(-  electrode, 
if  it  be  of  gold.  (2.)  Electrolysis  cannot  happen  unless 
the  fluid  be  a  conductor  of  electricity ;  and  no  solid  body, 
however  good  a  conductor,  has  ever  been  thus  decomposed. 
A  plate  of  ice,  however  thin,  interposed  between  the  elec- 
trodes, will  entirely  prevent  the  passage  of  the  power;  but 
the  electrolysis  will  proceed  as  soon  as  the  least  hole  melts 
in  the  ice,  through  which  the  power  can  pass.  Fluidity  is 
therefore  a  very  essential  condition  of  electrolysis.  The 
fluidity  may  be  that  of  heat,  or  of  solution;  thus,  the 


Explain  the  terras  electrode,  electrolysis,  and  electrolyte.  What  are 
ions?  228.  Are  all  compounds  electrolytes?  Give  examples.  What 
is  the  second  condition  of  electrolysis  ?  Give  examples. 


ELECTRO-CHEMICAL  DECOMPOSITION.  145 

chlorids  of  lead,  silver,  and  tin  are  not  electrolysed  in  a 
solid  state,  but  when  fused  they  are  decomposed  with  ease. 
(3.)  The  ease  of  electro-chemical  decomposition  seems  in 
a  good  degree  propoitioned  to  the  conducting  power  of  the 
fluid.  Thus,  pure  water  is  by  no  means  a  good  conductor, 
and  its  electrolysis  is  difficult;  but  the  addition  to  it  of  a 
few  drops  of  sulphuric  acid,  or  of  some  other  soluble  con- 
ductor, greatly  promotes  the  ease  with  which  it  is  decom- 
posed. (4.)  The  amount  of  electrolysis  is  directly  propor- 
tioned to  the  quantity  of  electricity  which  passes  the  elec- 
trodes. (5.)  The  binary  compounds  of  the  elements,  as 
a  class,  are  the  best  electrolytes.  Water  and  iodid  of 
potassium  are  instances;  while  sulphuric  acid,  which  has 
three  equivalents  of  base  to  one  of  acid,  is  not  an  electro- 
lyte. No  two  elements  seem  capable  of  forming  more  than 
one  electrolyte.  (6.)  Most  of  the  salts  are  resolvable  into 
acid  and  base.  Thus,  sulphate  of  soda  is  resolved  into  sul- 
phuric acid,  which  appears  at  the  -|-  electrode,  and  will 
there  redden  a  vegetable  blue;  and  the  soda  which  appears 
at  the  —  electrode  will  restore  the  previously  reddened 
blue ;  so  that  by  reversing  the  direction  of  the  current, 
these  striking  effects  are  also  reversed, 

229.  (7.)  A  single  ion,  as  bromine,  for  instance,  has  no 
disposition  to  pass  to  either  of  the  electrodes,  and  the  cur- 
rent has  no  effect  upon  it.  There  can  be  no  electrolysis 
except  when  a  separation  of  ions  takes  place,  and  the  se- 
parated elements  go  one  to  each  electrode.  (8.)  There 
is  no  such  thing,  in  fact,  (as  has  been  often  supposed,) 
as  an  actual  transfer  of  ions  from  one  part  of  the  fluid  to 
cither  electrode.  In  the  case  of  water,  for  example,  oxygen 
is  given  out  on  one  side,  and  hydrogen  on  the  other.  In 
order  that  this  may  be  the  case,  there  must  be  water  be- 
tween the  electrodes.  We  cannot  believe  that  the  separa- 
tion of  the  elements  takes  place 
at  the  electrode  where  one  ele- 

.         •  -I  T  1       ,  1  i        ,   1 

nient  is  evolved,  and  that  the 
other  travels  over  unseen  to  the 
opposite  electrode.  We  may,  Fio.  9Q9 

(3.)  To  what  is  the  ease  of  the  electrolysis  proportioned?  (4.)  TG 
what  is  its  amount  owing  ?  (5.)  What  class  of  compounds  are  the  best 
electrolytes?  Give  examples.  (6.)  What  of  salts?  Give  examples. 
229.  (7.)  What  is  said  of  a  single  ion?  (8.)  What  of  the  transfer  of 
ions  ?  Give  the  explanation  offered  of  the  decomposition  of  water. 
10 


146  ELECTRICITY. 

however,  conceive  of  water  in  its  quiet  state,  as  represented 
by  the  diagram,  (fig.  202,)  each  molecule  being  firmly 
united  lay  polar  attractions  (218)  to  every  other,  and  that 
the  electrolytic  force  of  the  electric  current  has  power  to 
disturb  this  polar  equilibrium,  each  molecule  being  simi- 
larly affected.  In  this  case  the  electrolysis  will  proceed 
from  particle  to  particle  through  the  whole  chain  of  affini- 
ties, decomposing  and  recomposing,  until  the  ultimate  parti- 
cle on  each  side,  having  no 
polar  force  to  neutralize 

^  escaPes  at  that  ele°- 

trode  which  has  a  polarity 
._.  0  opposite  to  itself.  This 

explanation  may  be  better 
understood,  perhaps,  by  inspecting  the  second  diagram,  (fig. 
203,)  which  represents  a  series  of  compound  molecules  of 
water  undergoing  electrolysis,  the  H  and  0  being  eliminated 
at  the  opposite  extremities.  The  same  explanation  will  be 
found  to  serve  for  all  other  cases  of  electrolysis,  both  simple 
and  secondary. 

230.  (9.)  A  surface  of  water,  and  even  of  air,  has  been 
shown  capable  of  acting  as  an  electrode,  proving  that  the 
contact  of  a  metallic  conductor  with  the  decomposing  fluid 
is  not  essential.     The  discharge  from  a  powerful  electrical 
machine  was  made   to   pass   from  a  sharp  point  through 
air  to  a  pointed  piece  of  litmus  paper  moistened  with  sul- 
phate of  soda,  and  then  to  a  second  piece  of  turmeric  paper 
similarly  moistened.     This  discharge  had  power  to  effect  a 
true  electrolysis;  the  blue  litmus  was  reddened  by  the  sul- 
phuric acid  set  free  from  the  sulphate  of  soda,  while  the 
yellow  turmeric  was  turned  brown  by  the  alkaline  soda  from 
the  same  salt. 

231.  (10.)  Electrolysis  takes  place  in  a  series  of  com- 
pounds in  the  precise  order  of  their  equivalents.     Thus,  if 
wine-glasses  are  arranged  in  a  series,  and  in  one  is  placed 
sulphate  of  soda,  in  another  acidulated  water,  in  another 
iodid  of  potassium,  and  in  another  hydrochloric  acid,  and  if 
the  whole  series  be  connected  together  by  siphon  tubes,  or 
moistened  lampwick,  passing  from  glass  to  glass,  and  a 

230.  (9.)  What  is  said  of  electrolysis  without  metallic  conductors? 
Explain  the  experiment  of  the  electrolysis  of  sulphate  of  soda  by  the 
electrical  machinfc.  231.  How  does  electrolysis  occur  in  a  series  of  com- 
pounds ? 


ELECTRO-CHEMICAL   DECOMPOSITION.  147 

powerful  galvanic  current  be  then  passed  through  them, 
electrolysis  will  occur  in  all,  but  unequally. 

It  has  been  proved  by  acccurate  experiment,  that  the 
decomposition  which  ensues  is  in  exact  proportion  to  the 
equivalents  of  each  substance.  In  other  words,  we  may  say 
it  requires  one  equivalent  of  electricity  to  decompose  one 
equivalent  of  an  electrolyte  formed  from  the  union  of  an 
equivalent  of  acid  and  another  of  base.  Conversely,  from 
the  fact  that  an  equivalent  of  electricity  is  required  to  de- 
compose any  compound,  it  is  proved  that  the  opposite  ele- 
ments of  this  compound,  in  uniting,  will  disengage  the  same 
equivalent  of  electricity. 

232.  (11.)   The  passage  of  a  current  within  the  cells  of  a 
voltaic  battery  depends  also  upon  the  decomposition  in  each 
cell,  equally  with  that  between  the  platinum  electrodes. 
The  same  phenomena  which  we  notice  in  the  decomposing 
cell  (224)  take  place  also  in  each  battery  cell.     Water  is 
decomposed,  and  the  hydrogen  is  given  off  from  the  positive 
plate,  while  the  oxygen  combines  with  the  zinc,  and  thus 
escapes  detection.     Therefore,  no  fluid  not  an  electrolyte  is 
suitable  to  excite  a  battery.     Acid  water  acts,  for  this  pur- 
pose, only  by  the  decomposition  of  the  water  and  oxydation 
of  the  zinc.     The  presence  of  the  acid  is  useful  only  so  far 
as  it  combines  with  the  oxyd  of  zinc  constantly  accumulating 
on  the  zinc  plate,  which  must  be  removed  as  fast  as  formed, 
in  order  to  keep  up  a  steady  flow  of  electricity. 

233.  The  theories  which  have  been  proposed  to  account 
for  electro-chemical  decomposition  and   the  action  of  the 
voltaic  circuit,  we  cannot  discuss  here,  any  further  than  to 
say  that  the  chemical  theory  first  proposed  by  Dr.  Wollaston 
is  now  generally  accepted.     Volta  argued  that  the  contact 
of  different  metals  was  essential  to  the  production  of  a  cur- 
rent.    The  researches  of  Faraday,  however,  in  confirming 
the  chemical  view  of  Wollaston,  have  completely  disproved 
the  contact  theory.     A  very  simple  experiment  by  Faraday 
illustrates  this  statement.     A  slip  of  amalgamated  sheet 
zinc  bent  at  a  right  angle  is  hung  in  a  glass  of  dilute  acid; 
on  it  is  laid  a  folded  piece  of  bibulous  paper  moistened  with 

In  other  words,  what  do  we  say  ?  Conversely,  what  ?  232.  How 
does  a  current  pass  in  the  cells  of  a  battery  ?  What  happens  in  each 
cell  ?  What  is  requisite  in  the  fluid  used  to  excite  a  battery  ?  How 
does  acid  water  act  in  the  battery?  233.  What  two  theories  have  been 
proposed  to  account  for  the  electrical  phenomena  of  electrolysis?  What 
tjitnple  experiment  disproves  the  contact  theory  ? 


148 


ELECTRICITY. 


iodid  of  potassum.  A  .platinum  plate,  with  an 
attached  wire  of  the  same  metal,  is  now  placed  in 
the  acid  water,  but  not  in  contact  with  the  zinc; 
the  sharpened  end  of  the  wire  is  bent,  so  as  to 
touch  the  moistened  paper,  and  very  soon  it  is 
discolored  by  a  brown  spot  made  by  the  freo 
iodine,  liberated  from  the  electro-chemical  de- 
composition of  the  iodid  of  potassium,  with  which 
the  paper  is  moistened.  There  is  no  contact  of 
metals,  and  the  current  is  excited  only  from  the 
Fig.  204,  decomposition  of  the  iodid  out  of  the  cell,  and  of 
the  water  in  it.  A  very  strong  argument  in  favor  of  the 
chemical  theory  has  been  before  mentioned,  that  the  di- 
rection of  the  current  is  always  determined  by  the  nature 
of  the  chemical  action — the  metals  most  acted  on  being 
always  positive. 

234.  The  electrotype,  or  deposition  of  metals  from  their 
solution  by  the  voltaic  current,  seems  to  have  been  suggested 
by  Daniell's  battery.  It  has  been  remarked,  that  the  cop- 
per of  the  sulphate  of  copper  in  the  outer  cell  of  that  battery 
is  deposited  in  a  metallic  state.  The  procuring  of  a  pure 
metal  in  a  perfectly  malleable  state,  by  means  of  a  current 
of  electricity,  is  a  most  important  fact,  and  has  given  rise 
to  a  new  and  valuable  art,  which  has  become  wonderfully 
extended  in  its  applications.  We  thus  accomplish,  in  fact, 
a  cold  casting  of  copper,  silver,  gold,  zinc,  and  many  other 
metals;  and  a  new  field  of  great  extent  has  been  thus 
opened  for  the  application  of  metallurgic 
processes.  The  tinting  of  metals  of  various 
hues  by  metallic  oxyds,  and  the  coloring  of 
their  surfaces  by  palladium,  are  among  the 
most  surprising  of  its  effects.  The  very 
simple  apparatus  required  to  show  these  re- 
sults experimentally,  is  represented  in  the 
figure,  (205.)  It  is  nothing,  in  fact,  but 
a  single  cell  of  Daniell's  battery.  A  glass 
tumbler  S,  a  common  lamp-chimney  P, 
with  a  bladder-skin  tied  over  the  lower  end 
and  filled  with  dilute  acid,  is  all  the  appara- 
lg'  '  tus  required.  A  strong  solution  of  sulphate 
of  copper  is  put  in  the  tumbler,  and  a  zinc  rod  Z  in  P, 


234.  What  is  the  electrotype?     Explain  its  uses. 


ELECTRO-CHEMICAL   DECOMPOSITION.  149 

the  moulds,  or  casts,  m  m  are  seen  suspended  by  wires 
attached  to  the  binding  screw  of  Z.  Thus  arranged,  the 
copper  solution  is  slowly  decomposed,  and  the  metal  is 
evenly  and  firmly  deposited  on  m,  m.  A  perfect  reverse 
copy  of  m  is  thus  obtained  in  solid,  malleable  copper.  The 
back  of  m  is  protected  by  varnish,  to  prevent  the  ad- 
hesion of  the  metallic  copper  to  it.  In  this  manner  the 
most  elaborate  and  costly  medals  are  easily  multiplied,  and 
in  the  most  accurate  manner.  In  practice,  casts  are  made 
in  fusible  metal  of  the  object  to  be  copied,  and  the  operation 
is  conducted  in  a  separate  cell,  containing  only  the  sulphate 
of  copper,  one  of  Smee's  batteries  supplying  the  power. 
The  art  is  also  now  extensively  applied  to  plating  in  gold 
and  silver  from  their  solutions ;  the  metals  thus  deposited 
adhering  perfectly  to  the  metallic  surface  on  which  they  are 
deposited,  provided  these  be  quite  clean  and  bright 

All  the  copper-plates  of  the  charts  of  the  Coast  Survey  are 
reproduced  by  the  electrotype — the  originals  are  never  used 
in  the  press,  but  only  the  copies,  and  any  required  number 
of  these  may  be  produced  at  small  expense. 


150 


PART  II.— CHEMICAL  PHILOSOPHY. 
ELEMENTS  AND  THEIR  LAWS  OF  COMBINATION. 

235.  THE  number  of  elements,  (or  simple  substances,)  as 
DOW  recognized,  is  sixty-two,  forty-nine  of  which  are  metals 
The  elements  are  usually  divided  into  metals  and  metalloids, 
or  non-metallic  substances.  This  convenient  distinction  is 
not  strictly  accurate,  since  there  are  several  elements,  as 
tellurium,  carbon,  arsenic,  silicium,  and  others,  which  seem 
to  possess  an  intermediate  character.  The  term  metalloid 
is  therefore  preferable.  Only  fourteen  of  the  elementary 
bodies  are  of  common  occurrence,  and  of  these  the  atmo 
sphere,  water,  and  the  great  bulk  of  the  planet  are  com- 
posed. The  remainder  are  comparatively  rare,  and  are  known 
only  to  the  chemist.  Of  these,  twenty-one,  marked  in  the 
table  with  an  asterisk  (*),  will  not  be  discussed  in  this  work, 
or  will  be  very  briefly  considered,  because  of  their  great  rarity, 
and  the  difficulty  of  procuring  the  substances  containing 
them. 

23G.  At  common  temperatures,  and  when  set  free  from 
combination,  nearly  all  the  elements  are  solids.  Two,  mer- 
cury and  bromine,  are  fluids,  and  five  are  gases,  namely, 
chlorine,  fluorine,  hydrogen,  oxygen,  and  nitrogen.  A  few 
only  of  the  elements  are  found  naturally  in  a  free  or  un- 
combined  state,  among  which  we  may  name  oxygen,  nitro- 
gen, carbon,  sulphur,  and  nine  or  ten  metals.  All  the  rest 
exist  in  combination  with  each  other,  and  so  completely 
disguised  as  to  manifest  none  of  their  properties. 

237.  The  names  of  the  elements  are  arbitrary  or  conven- 
tional, while  the  nomenclature  of  their  compounds  is  sub- 
ject to  the  strictest  laws.  Some  of  the  elementary  bodies 
have  been  known  from  the  remotest  antiquity,  and  were  in 
common  use  long  before  the  science  of  chemistry  was  heard 
of.  Thus  several  metals,  as  Copper,  (Cuprum,)  Gold, 
(Aurum,)  Iron,  (Ferrumf)  Mercury,  (Hydrargyrum^)  Sil- 


235.  What  is  the  number  of  elements?  How  divided?  What  occupy 
an  intermediate  position  ?  236.  What  is  the  physical  condition  of  the 
elements  ?  Which  are  fluid  ?  Which  gaseous  ?  Which  found  uncom- 
bined  ?  237.  What  of  the  names  of  elements  ?  Which  have  been  long 
known  ? 


ELEMENTS— LAWS   OP   COMBINATION.  151 

ver,  (Argentum,)  Lead,  (Plumbum,}  Tin,  (Stannum,)  have 
long  been  known  either  by  the  names  we  now  give  them,  or 
by  those  Latin  terms  of  which  our  English  names  are  trans- 
lations. The  alchemists  named  the  metals  after  the  various 
planets.  Thus,  Gold  was  called  Sol,  the  Sun ;  Silver,  Luna, 
the  Moon;  Iron,  Mars;  Lead,  Saturn;  Tin,  Jupiter;  Quick- 
silver, Mercury ;  and  Copper,  Venus.  Hence,  formerly  the 
astronomical  signs  or  symbols  of  these  planets  were  employed 
to  represent  the  names  of  these  metals,  and  they  are  still  in 
use  in  some  countries. 

Several  of  the  elements  have  been  named  from  some 
prominent  or  distinguishing  physical  property  of  color,  taste, 
or  smell,  which  they  possess :  thus,  Bromine  is  so  called 
from  the  Greek  word  bromos,  fetor;  Chlorine,  from  chloros, 
green,  in  allusion  to  its  greenish  color;  Chromium,  from 
chroma,  color,  because  it  makes  highly-colored  compounds, 
as  chrome-yellow;  Glucinum,  from  glukus,  sweet,  from  the 
sweet  taste  of  its  salts ;  Iodine,  from  ion,  a  violet,  and  eidos, 
in  the  likeness  of.  Another  class  of  names  has  been  con- 
trived from  what  was  supposed  to  be  the  characteristic  at- 
tribute of  the  body  in  combination.  Thus,  Oxygen  was  so 
named  because  many  of  its  compounds  are  acids,  from  the 
Greek,  oxus,  acid,  and  gennao,  I  produce.  Hydrogen  is 
from  hudor,  water,  and  gennao,  I  produce. 

238.  It  has  been  discovered  that  the  elements,  in  corn- 
Dining  among  themselves,  unite  always  in  certain  weights,  in- 
variable in  each  case,  and  supposed  to  have  an  immediate  re- 
lation to  the  atomic  constitution  of  the  substance.  These 
weights  represent  respectively  the  quantities  in  which  the 
elements  unite  with  each  other,  and  they  are  called  equiva- 
lent atomic  weights  or  combining  numbers.  In  the  follow- 
ing table,  the  equivalent  or  combining  numbers  of  all  the 
elementary  bodies  are  given  in  accordance  with  the  latest 
and  best  authorities.  Because  hydrogen  enters  into  combi- 
nation with  other  bodies  in  a  smaller  weight  than  any  other 
known  element,  it  has  generally  been  used  in  Great  Britain 
and  in  this  country  as  the  basis  of  the  scale  of  equivalent 
numbers.  It  is  supposed  also,  by  some  good  chemists,  that 
the  numbers  expressing  the  combining  weights  of  all  bodies 


What  of  astronomical  signs  ?  Whence  such  names  as  bromine,  Hy- 
drogen ?  Iodine,  &c.  ?  238.  How  do  the  elements  unite  ?  What  do  the 
weights  represent  ?  What  are  they  called  ?  Why  is  hydrogen  unity  ? 


152 


ELEMENTS — LAWS    OF   COMBINATION. 


•would  be  found,  on  more  accurate  research,  to  be  simple 
multiples  of  the  unit  of  hydrogen.  If  this  view  were  cor- 
rect, it  would  give  us  the  great  convenience  of  avoiding 
fractional  numbers.  The  latest  investigations  have  so  far 
confirmed  this  idea,  that  in  the  present  edition  of  this  work 
a  largely  increased  number  of  elements  stand  with  simple 
numbers.  Berzelius  determined  more  atomic  numbers  than 
any  other  chemist,  and  his  labors  have  in  most  cases  stood 
the  severest  review,  and  deserve  the  everlasting  gratitude  of 
chemists.  Most  chemists  of  continental  Europe  assume 
oxygen  as  100;  therefore,  to  convert  the  numbers  of  the  fol- 
lowing table  to  the  oxygen  scale,  multiply  them  by  12*5. 

TABLE     OF     ELEMENTARY    SUBSTANCES,    WITH     THEIR     SYMBOLS     AND 
ATOMIC    WEIGHTS    OR    EQUIVALENTS. 


Name. 

Svra-   1 
bo!. 

II  =:  I. 

Name. 

Svm- 
bol. 

Nl 

H=l- 

29-6 

Al 
Sb 
As 
Lin 
Be 
Hi 
B 
Br 
CJ 
Ca 
0 
Ce 
Cl 
Cr 
Co 
Cm,Ta 
Cu 
D 
B 
Fl 
Au 
U 
I 
Ir 
Fe 
La 
Pb 
Li 
Mg 
Mn 
Hg 

13-7 
12'.)- 
75' 
68-50 
47 
208' 
10-9 
80' 
56' 
20- 
6- 
47' 
35.50 
26-7 
29-5 
184- 
31-7 

Ki- 
rn- 
1- 
127- 
99- 
28- 
36* 
103-5 
6-5 
12-2 
27-6 
100- 

Niokol 

Antimony  (Stibium)  

Molybdenum  
*Xiobium 

Mo 
Nb 

N 
Xo 
<)s 
O 
Pd 
Pe 
P 
Pt 
K 
Jt 
11  u 
Se 
Si 
Ag 
Na 
Sr 

^ 

To 
Tli 
Th 
Su 
Ti 
W 
II 
V 
Y 
Zn 
Zr 

46- 
14- 

90-6 
8- 
53-3 

98-7 

52-2 
52-2 
40- 
21-3 
108- 

44- 
16- 
64- 

iV.rtj 

•r)!,t- 

yo- 
no- 

68-0 

32-5 

22-4 

Bari  um  

Nitrogen  

*Bery  Ilium  (Gluciuum)... 
Bismuth 

Boron  

Oxygen  
*Pniladiuin 

|  Cadmium  
Calcium    

*Ccrium  

Potassium  (Kalium)  
:  *Hhodium  

Cobalt 

*Co!  u  mbi  u  m  (Tan!  al  um) 

'  Silieium  

I  Silver  (Argon  turn)  
Folium  (Natrium) 

*  Did  vmium  
#Erbium 

Strontium  
:  Sulphur  

Fluorine  
Gold  (Auruni)  

I  *Terbium  

Iodine  

*Thorium  
i  Tin  (Stannum)  

i  *Titanium  

•••'Lantaniuni  
Load  (Plumbum)  
Lithium 

*Tungsten(^Yolfrarnium) 

*Vana/lium  

WuKiicsinni  

*Yttrium  

7inc 

*Zirconium  

i 

Combination  by  Weight. 

239.  The  laws  by  which  the  elements  unite  to  form  com- 
pounds, are  included  in  the  four  following  propositions : — • 

What  of  its  multiple  relations  ?   Who  determined  most  atomic  weights  ? 


COMBINATION   BY  WEIGHT.  153 

1st.  The  law  of  definite  proportions,  or,  a  compound  of 
two  or  more  elements,  is  always  formed  by  the  union  of 
certain  definite  and  unalterable  proportions  of  its  constituent 
elements. 

2d.  The  law  of  multiple  proportions,  which  requires  that 
when  two  bodies  unite  in  more  proportions  than  one,  these 
proportions  bear  some  simple  relation  to  each  other. 

3d.  The  law  of  equivalent  proportions,  according  to  which 
when  a  body  (A)  unites  with  other  bodies,  (B,  C,  D,  &c.,) 
the  proportions  in  which  B,  C,  and  D  unite  with  A  shall 
represent  in  numbers  the  proportions  in  which  they  will 
unite  among  themselves,  in  case  such  union  takes  place. 

4th.  The  law  of  the  combining  numbers  of  compounds, 
by  which  the  combining  proportion  of  a  compound  body  is 
the  sum  of  the  combining  weights  of  its  several  elements. 

240.  These  general  laws  of  combination  are  subject  to 
some  modifications,  which  will  be  explained  as  they  arise. 
The  first  of  the  laws  above  given  is  the  result  of  chemical 
analysis,  and  is  proved  by  synthesis.    Thus,  from  nine  grains 
of  water  we  obtain  eight  grains  of  oxygen  and  one  of  hydro- 
gen, and  by  the  union  of  the  like  weights  of  these  two  sub- 
stances we  obtain  nine  grains  of  water.     Constancy  of  com- 
position is  the  essential  feature  of  chemical  compounds. 

By  the  law  of  multiple  proportions,  we  learn  that  if  a  body 
(A)  unites  with  a  body  (B)  in  more  proportions  than  one, 
these  proportions  bear  a  simple  relation  to  each  other. 
Thus,  we  may  have  the  series  of  compounds  A  -f-  B  :  A  -j-  2B 
:  A  -}-  3B  :  A  -f-  4B  :  A  -f-  5B,  as  in  the  case  of  nitrogen 
and  oxygen,  between  which  this  very  series  occurs,  forming 
five  distinct  compounds,  in  which  one,  two,  three,  four,  and 
five,  parts  by  weight  (atoms)  of  oxygen  unite  with  one  of 
nitrogen.  (2.)  In  place  of  this  simple  ratio  we  may  have 
one  intermediate  :  thus,  the  expressions  2 A  -j-  3B  :  2A  -j- 
5B  :  2A-J-7B  represent  a  series  of  compounds  which 
are  equal  to  the  fractional  ratios  1  :  1£,  1  :  2J,  1  :  3i. 

241.  As  by  chemical  analysis  the  law  of  definite  proportions 
is  established,  so  by  the  same  direct  experimental  method  do 
we  prove  the  law  of  equivalent  proportions.     Oxygen  is  an 
element  forming  at  least  one  definite  compound  with  every 

239.  What  is  the  1st  law  of  combination  ?  The  2d  ?  The  3d  ?  The  4th  ? 
240.  Whence  is  law  1st  derived?  Give  an  example  ?  What  of  the  law  of 
multiple  proportions?  Give  examples  of  the  2d  modification?  241.  How  is 
the  law  of  equivalent  proportions  demonstrated  ?  What  is  said  of  oxygen  ? 


154  ELEMENTS — LAWS   OF   COMBINATION. 

other  element  known  except  fluorine.  These  compounds  are 
termed  oxyds,  (246.)  By  analysis  we  find  that  water  always 
contains  in  100  parts  11-11  parts  of  hydrogen  and  88-89  parts 
of  oxygen.  If  we  ask  how  much  oxygen  is  proportional, 
or  equivalent  to  a  unit  of  hydrogen,  we  state  the  simple 
proportion  11-11  :  100  : :  88-89  :  x  in  which  x  =  8,  which 
is  therefore  the  equivalent  of  oxygen.  In  like  manner,  we 
might  go  on  making  analyses  of  all  the  compounds  of  oxygen 
until  we  had  completed  the  whole  list,  when  we  should  have 
a  table  of  equivalents  for  all  the  elements,  hydrogen  being 
unity.  Thus, 

16  parts  of  sulphur, 
6  parts  of  carbon, 
1  part  of  hydrogen, 

8  parts  of  oxygen  unite  with  -j    35-5  parts  of  chlorine, 
100  parts  of  mercury, 
28  parts  of  iron, 
14  parts  of  nitrogen. 

Of  course,  16,  6,  1,  35.5,  100,  28,  and  14,  are  respec- 
tively the  equivalents  of  sulphur,  carbon,  hydrogen,  chlo- 
rine, mercury,  iron,  and  nitrogen.  Chemical  equivalent  and 
atomic  weight  have  the  same  meaning  in  this  work. 

242.  If  any  of  those  bodies  unite  to  form  compounds,  the 
union  will  always  happen  in  quantities  by  weight  exactly 
proportional  to  those  numbers.  Thus,  hydrogen  (1)  unites 
with  chlorine  (35-5)  to  form  chlorohydric  or  muriatic  acid. 
In  36-5  pounds,  therefore,  of  this  acid,  there  Avill  be  1  pound 
of  hydrogen  and  35-5  pounds  of  chlorine.  If  sulphur  com- 
bines with  mercury,  it  will  require  16  parts  of  sulphur  and 
100  parts  of  mercury,  and  there  will  be  116  parts  of  sul- 
phuret  formed;  or  it  may  require  32  parts  of  sulphur  to 
100  parts  of  mercury,  when  we  should  have  a  bisulphurct.  If 
oxygen  is  assumed  as  the  standard  of  comparison  for  atomic 
weights,  then,  calling  it  100,  hydrogen  will  be  12-5,  and  all 
the  other  elements  will  have  numbers  just  twelve  and  a  half 
times  as  large  as  their  equivalents  on  the  hydrogen  scale. 

It  follows,  as  a  necessary  result  of  this  law  of  equivalent 
proportions,  that  the  combining  numbers  of  a  compound 
should  be  the  sum  of  the  equivalents  of  its  constituents. 

Give  the  mode  of  determining  atomic  weights  ?  Give  some  examples  ? 
What  is  the  meaning  of  chemical  equivalent?  Of  atomic  weight? 
242.  What  is  tho  relation  among  elements  in  combination?  How  is  it 
in  chlorohydric  acid  ?  In  sulphurct.  of  mercury  ?  What  of  tho  combining 
numbers  of  compounds  ? 


NOMENCLATURE   AND    SYMBOLS.  155 

Chemical  Nomenclature  and  Symbols. 

243.  It  would  have  been  a  hopeless  task  for  the  strongest 
memory  to  retain  all  the  names  of  chemical  compounds,  if 
they  had — like  the  names  of  the  elements — been  bestowed 
by  the  caprice  of  those  who  first  discovered,  or  described 
them.     A  committee  of  the  French  Academy,  with  Lavoi- 
sier at  their  head,  in  1787,  settled  the  principles  of  chemi- 
cal nomenclature,  which  endure  to  this  day,  although  the 
actual  state  of  the  science  requires  great  changes  in  them. 
All  chemical  compounds  are  made  to  derive  their  names  from 
one  or  more  of  their  constituents.     Before  stating  the  rules 
of  nomenclature,  we  must  define  certain  general  terms  of 
common  occurrence. 

244.  Bodies  are  divided  into  acids,  bases,  and  salts.    Salts 
result  from  the  union  of  acids  with  bases.    By  the  voltaic  pile 
salts  are  decomposed  (228  [6])  into  acids  and  bases — the 
acids  go  to  the  positive  pole,  the  bases  to  the  negative.     We 
therefore  call  the  acid,  in  reference  to  electrical  law,  the 
electro-negative  constituent,  and  the  base  the  electro-positive. 
This  is  equally  true  of  those  compounds  which  render  up 
their  elements  in  electrolysis  as  of  salts  which  are  simply 
separated  into  acids  and  bases:  c.  <j.  common  salt  by  elec- 
trolj'sis  yields   chlorine,  an   electro-negative  element,  and 
sodium,  an  electro-positive  one.     The  former  is  an  acid,  the 
latter  a  base. 

Acids  and  bases  are  further  distinguished,  in  that  acids 
redden  the  blue  vegetable  infusions,  while  bases  restore  the 
colors  which  the  acids  have  reddened.  Some  vegetable 
colors,  like  syrup  of  violets,  or  tincture  of  dahlia  or  of  pur- 
ple cabbage,  are  made  green  by  alkalies,  and  are  reddened 
by  acids.  If  no  change  of  this  sort  is  indicated,  the  body  is 
said  to  be  neutral. 

245.  When  two  elements  unite,  the  product  is  called  a 
binary  compound,  from  bis,  twice ',  thus  water,  sulphuric 
acid,  oxyd  of  silver,  and  oxyd  of  iron,  are  binary  compounds. 
Compounds  of  binary  combinations  with  each  other,  as  of 

243.  What  of  the  names  of  compounds  ?  Who  settled  the  principles 
of  nomenclature  ?  How  are  the  names  divided  ?  2-14.  How  are  bodies 
divided  ?  How  are  salts  formed  ?  What  of  the  pile  ?  What  docs  electro- 
positive mean  ?  What  electro-negative  ?  How  of  common  salt  ?  How 
are  acids  and  bases  further  distinguished?  What  is  neutrality?  245 
What  is  a  binary  compound? 


156  ELEMENTS — LAWS   OF   COMBINATION. 

sulphuric  acid  with  soda,  forming  sulphate  of  soda,  or  Glau- 
ber's salts,  are  called  ternary  compounds,  (from  ter,  thrice.) 
Compounds  of  salts  with  each  other,  (as  in  the  case  of  alum, 
which  is  a  compound  of  sulphate  of  potash  and  sulphate  of 
alumina,)  are  named  quaternary  compounds,  from  guatuorj 
four. 

246.  The  compounds  of  oxygen  are  called  either  oxyds 
or  acids :  thus,  water  is  an  oxyd  of  hydrogen ;  and  one  of  the 
oxygen   compounds  of  sulphur  is  called   sulphuric    acid. 
The  binary  compounds  of  chlorine,  bromine,  iodine,  fluo- 
rine, and  some  other  elements,  which  resemble  oxygen  in 
their  mode  of  combination,  are  also  distinguished  by  the 
same  termination  id  or  ide.     Thus,  chlorine  forms  chlorids; 
bromine,  bromids ;  iodine,  iodids ;  and  fluorine,  fluorids. 

The  binary  compounds  of  sulphur,  selenium,  phosphorus, 
arsenic,  and  some  others,  receive  usually  the  termination  uret. 
Thus  we  say  sulphuret,  selcniuret,  phosphuret,  &c.,  although 
sulphid,  selenid,  phosphid,  &c.7  are  more  in  obedience  to 
the  rules  of  the  nomenclature. 

247.  In  all  cases,  the  name  of  the  electro-negative  con- 
stituent of  a  compound  rules  the  name  of  the  genus  of  the 
compound.     Thus,  chlorid  of  potassium,  sulphuret  of  iron, 
and  sulphate  of  soda,  all  imply  that  the  chlorine,  sulphur,  or 
sulphuric  acid,   are  the   electro-negative  constituents,  and 
that  potassium,  iron,  and  soda  are  the  electro-positive  ele- 
ments in  those  compounds.     The  same  rule  holds  in  all  the 
salts  also,  however  complex. 

248.  When  the  same  element  unites  with  oxygen  in  more 
than  one   proportion,  forming   two   or.  more   oxyds,  then 
these  are  distinguished  as  protoxyd,  deutoxyd,  tritoxyd,  from 
the  Greek  protos,  first ;  deuteros,  second ;  and  tritos,  third  ; 
corresponding  to  the  first,  second,  and  third  degree  of  oxyda- 
tion.     The  word  bi  (double)  binoxyd  is  also  used  in  place  of 
deutoxyd.     The  oxyd  which  contains  the  largest  proportion 
of  oxygen  with  which  the  body  is  known  to  unite,  is  also  called 
the  peroxyd,  from  the  Latin,  per,  which  is  a  particle  of  in- 
tensity in  that  language.     Thus,  there  are  two  oxyds  of 
hydrogen,  the  protoxyd  (water)  and  the  pcroxyd.     There 

A  ternary?  A  quaternary  ?  246.  What  of  the  oxygen  compounds  ? 
How  of  the  compounds  of  chlorine,  &c.  ?  How  of  sulphur,  <fcc.  ?  247. 
What  of  the  electro-negative  constituent?  Give  examples.  248.  How 
are  the  first,  second,  third,  <tc.,  oxyds  distinguished  ?  What  are  bi- 
noxyds  ? 


NOMENCLATURE  AND  SYMBOLS.         157 

are  three  oxyds  of  manganese :  1.  The  protoxyd;  2.  Tho 
deutoxyd  ;  3.  The  peroxyd  of  manganese.  Some  oxyds  are 
formed  in  the  proportion  of  2  to  3,  or  once  and  a  half. 
Such  oxyds  are  distinguished  by  the  term  sesquioxyds,  from 
the  numeral  sesqui,  (once  and  a  half.)  Certain  inferior 
oxyds  are  called  suboxyds,  as  suboxyd  of  copper,  Cu20. 

249.  The  acid  compounds  of  oxygen  derive  their  names 
by  adding  the  terminations  ous  or  ic  with  the  word  add  to 
the  electro-negative  constituent.     Thus,  for  the  two  acids  of 
sulphur  we  have  sulphurous  acid  and  sulphuric  acid  :  the 
first  signifies  the  lowest,  the  second  the  highest  oxygen 
compounds  of  the  substance  known  at  the  time  when  the 
rules  of  the  nomenclature  were  framed.     As  the  progress  of 
science  has  made  known  other  and  intermediate  compounds, 
in  order  to  bring  them  into  the  system,  it  was  necessary  to 
employ  the  terms  hypo  and  hyper,  from   hupo,  under,  and 
huper,  above.     Thus,  we  have  hyposulphurous  and  hyper- 
sulphurous,  for  two  acids  of  sulphur  respectively  under  and 
above  sulphurous  in  their  quantities  of  oxygen.     The  pre- 
fix per  has  been  added  to  signify  a  degree  of  oxydation 
higher  than  that  implied  by  ic.     Thus,  chloric  acid  was  for 
a   long  time  the  highest  known  degree  of  oxydation    of 
chlorine  ;  but  now  we  have  perchloric  acid  also.     Peroxyd 
means  the  highest  oxyd  known. 

250.  Sulphur,  selenium,  tellurium,  arsenic,  &c.,  and  chlo- 
rine, bromine,  iodine,  and  fluorine,  also  form  acid  compounds 
with  hydrogen.     These  are  named  after  the  electro-negative 
compounds,  sulphydric,  selenhydric,  chlorohydric,  bromohy- 
dric,  &c.     Sulphuretted  hydrogen,  arseniuretted  hydrogen, 
&c.,  are  also  used,  as  well  as  hydrochloric,  hydrobromic, 
&c. ;  but  the  first  named  are  more  in  accordance  with  the 
principles  of  the  nomenclature. 

251.  The  salts  (ternary  compounds)  are  named   in   an 
equally  simple  manner.     The  acid  supplies  the  generic,  the 
base  the  specific  name.     Sulphate  of  soda,  nitrate  of  potassa, 
sulphite  of  soda,  and  nitrite  of  potassa,  are  respectively  salts 
of  sulphuric,  nitric,  sulphurous,  and  nitrous  acids.     Thus, 

What  sesquioxyds  ?  Suboxyds  ?  249.  How  are  the  acid  compounds 
of  oxygen  named  ?  What  of  hypo  and  hyper  ?  What  of  the  prefix  per  ? 
Give  examples.  250.  How  are  acid  compounds  of  sulphur,  <fec.,  with 
hydrogen  named?  251.  How  are  salts  named  ?  What  gives  generic, 
and  what  specific  names  ?  How  do  the  acids  change  the  terminations 
ous  and  tc  ? 


158  ELEMENTS — LAWS    OF   COMBINATION; 

in  forming  salts,  the  acids  change  the  terminations  ous  and 
ic?  into  ite  and  ate. 

When  there  are  more  oxyds  of  a  base  than  one  entering 
into  combination,  the  resulting  salts  are  distinguished,  for 
example,  as  sulphate  of  the  protoxyd  of  iron  or  sulphate  of 
the  peroxyd. 

252.  Chemistry  enjoys  the  peculiar  advantages  of  possess- 
ing a  descriptive  and  denning  nomenclature.    Permanganate 
of  potassa  is  not  a  trivial  name,  but  supposing  that  we  now 
saw  it  for  the  first  time,  we  learn  from  its  simple  inspection 
that  the  compound  contains  permanganic  acid,  and  the  base 
potash ,  and  further,  that  the  acid  in  question  is  the  highest 
oxygen  compound  of  manganese  known. 

Convenient  as  the  nomenclature  of  chemistry  is,  the  pro- 
gress of  the  science  has  made  known  so  many  and  such 
complex  compounds,  that  it  long  since  became  necessary  to 
devise  some  simple  mode  of  notation  by  which  they  might 
be  expressed,  briefly  and  with  certainty.  Berzelius  sup- 
plied this  requisite  in  the  system  of  chemical  symbols,  by 
which  all  chemical  compounds  may  be  described  with  mathe- 
matical precision. 

253.  In   the   table   of    elementary   bodies,    (238,)    the 
"  symbols"  of  the  several  elements  will  be  found  opposite 
to  their  names.     The  symbols  are  merely  the  first  letter  of 
each  name,  or  the  first  two.     By  a  happy  thought,  Berzelius 
made  each  symbol  represent  not  merely  the  substance  for 
which  it  stands,  but  one  equivalent  of  each  substance.     Thus, 
0  stands  not  for  oxygen  in  general,  but  for  one  equivalent 
of  that  element;  or,  hydrogen  being  unity,  for  the  number 
8.     0  and  8  are  therefore  interchangeable  expressions,  white 
O2,  O3,  &c.  represent  2  X  8  and  3  X  8,  or  16  and  24. 

Compounds  are  represented  by  using  merely  the  symbols, 
and  sometimes  uniting  them  by  the  sign  of  addition,  (-]-.) 
Thus,  water  will  be  represented  by  HO,  or  one  equivalent 
of  each  element,  1  -|-  8  =  9,  the  combining  number  for 
water.  Protoxyd  of  lead  is  thus  written  PbO ;  and  PbO2  is 
the  peroxyd. 

The  co-efficient  attached  to  a  symbol  signifies  how  many 

When  there  are  more  oxyds  than  one,  how  is  it  ?     Give  examples. 

252.  What  advantage   of  nomenclature  has  chemistry  ?     Give  an  ex- 
ample.    What   inconvenience   was   found  ?     Who  supplied  the   want  ? 

253.  What  are   symbols  ?     What  do  they  express  ?     Give  an  instance. 
What  of  co-efficients  ? 


NOMENCLATURE  AND  SYMBOLS.        159 

atoms  of  the  element  are  concerned :  thus,  0,  O3,  O3,  O4,  O5, 
&c.,  are  respectively  1,  2,  3,  4,  and  5  atoms  of  oxygen,  which 
may  also  be  written  03,  03,  &c.,  or  20,  30,  40,  &c.^  For-' 
mules  are  expressions  by  which  we  recognize  the  constitution 
of  compounds;  thus,  sulphuric  acid  has  the  formula  S03,  oxyd 
of  iron  isFeO,  and  sulphate  of  protoxyd  of  iron  is  FeO-fS03, 
01  one  equivalent  of  that  compound.  Two  equivalents 
would  be  written  2(FeO-f-S03)-  If  we  write  2FeO+S03, 
it  means  two  atoms  of  protoxyd  of  iron,  plus  one  of  sul- 
phuric acid.  In  chemical  formulae,  the  electro-negative 
element  is  placed  last,  the  electro-positive  is  written  first. 
Thus  HO  is  water,  not  OH.  When  the  sign  plus  is  used 
in  a  chemical  expression,  it  usually  signifies  a  union  less 
close  than  if  a  comma  or  no  sign  at  all  had  been  used. 
Thus  S03  HO  -f-  2HO  signifies  a  hydrate  of  sulphuric  acid 
in  which  two  atoms  of  water  are  loosely  retained,  while  one 
is  in  more  close  combination. 

Water  unites  with  bases  to  form  hydrates,  as  the  common 
hydrate  of  potash  or  hydrate  of  lime,  and  also  with  acids 
to  form  compounds  analogous  to  salts.  Thus,  with  sulphu- 
ric acid,  forming  what  in  strictness  should  be  called  a  sul- 
phate of  water;  but  such  cases  are  usually  known  as  hydrated 
acids.  As  1, 2,  or  3  atoms  of  water  may  unite  with  an  acid, 
so  we  have  monohydrated,  bihydrated,  and  terhydrated  sul- 
phuric or  phosphoric  acids. 

254.  Since  chemical  analysis  only  makes  known  to  us 
the  number  of  constituents  found  in  a  compound,  and  the 
mode  in  which  these  are  arranged  is  undetermined,  except 
by  theoretical  considerations,  it  is  becoming  more  the  habit 
of  chemists  to  write  formulae  expressing  only  the  results  of 
analysis.     Thus,  acetic  acid  is  written  C4  H4  04,  since  this 
is  the  result  of  an  analysis  of  this  substance.     In  accord- 
ance with  some  views  it  is  written  C4  H3  03-fHO.     Sul- 
phuric acid,  usually  written  S03  HO,  is  written,  perhaps 
more  unexceptionably,  S04  H.     These  two  modes  of  expres- 
sion are  denominated  rational  and  empyrical  formulae. 

255.  Professor  Graham  suggests  what  he  calls  antithetic 
or  polar  formulae,  which  shall  place  all  the  electro-positive 
elements  of  a  compound  in  one  line,  and  all  the  electro- 

What  are  formulae  ?  Give  an  example.  Which  constituent  is  placed 
first?  What  of  sign  -j-  ?  Give  an  example.  What  of  hydrates  and 
acids?  254.  What  two  modes  of  stating  analytic  results  are  here  men- 
tioned ?  255.  What  are  antithetic  or  polar  formulae  ? 


160  ELEMENTS — LAWS    OF   COMBINATION. 

negative  in  a  line  above  them,  like  the  numerators  and  do- 
nominators  of  fractions.  Thus,  water  will  be  ^,  sulphuric 

,  03      .  ,          ,      ,     0  03        04 
acid  -7^,  sulphate  or  soda  ^p-  7^  or  r^r. 

S'  Na  S        NaS 

256.  The  symbols  are  sometimes  abbreviated  still  further, 
to  simplify  the  expression  of  very  complex  combinations. 
This  is  done  by  expressing  one  equivalent  of  oxygen  by  a 
dot,  two,  by  two  dots,  &c.     Thus,  S  signifies  the  same  as  S03, 
(dry  sulphuric  acid.)     Common  crystallized  alum  is  written 
in  full,  thus, 

Alfl08J3S08+KO,S03+24HO. 
We  can  conveniently  condense  this  long  expression ;  thus 

AJ  S8+KS+24H. 

The  short  line  under  the  Al  signifies  two  equivalents  of  the 
base.  Sulphur  is  in  like  manner  signified  by  a  comma; 
thus,  bisulphuret  of  iron,  Fe,Sa,  may  be  more  shortly 

written  Fe.  Symbolic  formulae  have  contributed  very  much 
to  the  progress  of  the  science,  and  are  invaluable  as  a  ready 
means  of  comparing  as  well  as  expressing  the  composition 
of  compound  bodies. 

257.  There  is  an  interesting  relation  between  the  atomic 
weights,  the  specific  gravities,  and  the  combining  measures 
or  volumes  of  those  elements  which  exist  in  the  gaseous 
state,  or  are  capable  of  assuming  it.     One  grain  of  hydro- 
gen occupies  46'7  cubic  inches,  but  the  same  bulk  or  volume 
of  chlorine  weighs  35-5  grains,  of  nitrogen  14  grains,  of 
iodine  127*1  grains,  of  bromine  80  grains,  and  of  oxygen 
16  grains.     These  weights  respectively  represent  the  density 
of  the  several  gases  compared  with  hydrogen  as  unity;  but 
they  are  also  identical  with  the  atomic  weights  of  the  seve- 
ral elements,  except  oxygen,  which  is  double.     We  have 
before  seen  (224)  that  two  volumes  of  hydrogen  and  one 
volume  of  oxygen  are  evolved  in  the  electrolysis  of  water. 
The  volumes  in  which  gaseous  elements  unite  are  therefore 
as  1  : 1  or  as  1 :  2,  or  some  simple  ratio.     Sulphur  has  ^ 
the  volume  of  oxygen  and  mercury  four  times.    The  combin- 

256.  How  are  symbols  abbreviated  ?  Illustrate  by  alum.  257.  What 
relation  is  named  between  bodies  in  the  gaseous  state  ?  Give  illustra- 
tions of  this.  How  do  elements  unite  by  volume  ? 


EXPANSION. 


161 


*ng  measure  of  oxygen  being  one  volume,  the  combining 
volume  of  hydrogen,  nitrogen,  chlorine,  bromine,  iodine, 
and  mercury,  will  be  two  volumes. 

258.  In  the  following  table,  hydrogen  is  taken  as  the 
unit  of  combining  measures,  and  we  observe  that  where 
the  numbers  in  the  second  column  are  the  same  as  the 
equivalents,  then  a  volume  represents  an  equivalent;  other- 
wise some  simple  multiple  of  it.  As  with  sulphur 
—96)  and  oxygen,  (2x8=16.) 


Gases  and  Vapors. 

Specific  Gravities. 

Chemical  Equivalents. 

Air=l. 

Hydrogen=l  . 

By  volume. 

By  weight. 

Hydrogen  

0-069 
0-972 
1-105 
2-421 
8-716 
5-544 
6-976 
6-617 

1- 
14. 
16- 
35-50 
127-1 
80- 
100- 
96- 

100  or  1 
100  or  1 
50  ori 
100  or  1 
100  or  1 
100  or  1 
200  or  2 
16 

1- 
14- 

8- 
35-50 

80- 
100- 
16- 

Oxveren. 

Chlorine  -  

Iodine  vapor  .  . 

Bromine  vapor  
Mercury  vapor  
Sulphur  vapor  

259.  The  combining  measure  of  compound  gases  is  vari- 
able, but  they  bear  a  simple  and  constant  ratio  to  each 
other ;  and  hence  the  density  of  a  compound  gas  may  often 
be  more  accurately  calculated  from  the  known  density  of 
its  constituents,  and  its  change  of  volume  in  combination, 
than  it  can  by  direct  experiment.  A  single  example  will 
illustrate  this.  Water  consists  of  1  atom  of  each  of  its 
constituents,  represented  by  1  volume  of  0  and  2  vo- 
lumes of  H.  These  three  volumes  weigh  1105-6-f-69-3 
-(-69 -3=1244-2  =  two  volumes  of  steam,  one  of  which  = 
half  this  sum,  or  622,  the  density  of  steam,  air  being  unity. 
From  a  comparison  of  the  experimental  results  obtained  by 
chemists,  it  appears  that  there  exists  a  very  simple  relation 
between  the  combining  measures  of  bodies  in  the  gaseous 
state,  compound  as  well  as  simple.  Of  a  few  bodies  the 
combining  measure  is  like  that  of  oxygen,  one  volume  ;  of 
a  large  number  double  that  of  oxygen,  or  two  volumes; 
of  a  still  larger  number  four  times  that  of  oxygen,  or  four 
volumes ;  while  combining  measures  of  three  and  six,  or  of 
fractional  portions  of  a  volume,  as  one-third,  are  compara- 


258.  Illustrate  this  further  from  the  table.      259.  How  in  compound 
gases?     What  is  the  case  with  water?     What  relations  are  established? 

11 


162  ELEMENTS — LAWS    OF   COMBINATION. 

tively  rare.  These  results  in  regard  to  combining  measures 
were  first  obtained  by  Humboldt  and  Gay-Lussac,  and  have 
aiforded  the  most  remarkable  confirmation  of  the  atomic 
theory  of  Dal  ton. 

260.  Atomic  volumes  are  those  numbers  which  are  ob- 
tained by  dividing  the  atomic  weights  of  bodies  by  their 
densities,  and  this  whether  we  speak  of  simple  or  compound 
bodies.     In  mineralogy,  as  shown  by  Dana,  this  relation  is 
often  of  great  importance  in  determining  the  relations  of 
species. 

Specific  Heat  of  Atoms. 

261.  Specific  heat  has  already  been   explained,   (117.) 
If  in  place  of  comparing  equal  weights  of  different  bodies 
together,  we  take  them  in  atomic  proportions,  we  shall  find 
the  numbers  representing  the  specific  heat  of  lead,  tin,  zinc, 
copper,  nickel,  iron,  platinum,  sulphur,  and  mercury,  to  be 
identical;  while  tellurium,  arsenic,  silver,  and  gold,  although 
equal  to  each  other,  will  be  twice  that  of  the  nine  previous 
bodies,  and  iodine  and  phosphorus  will  be  four  times  as 
much.     The  general  conclusion  drawn  from  these  and  other 
similar  facts  is,  that  the  atoms  of  all  simple  substances  have 
the  same  capacity  for  heat.     The  specific  heat  of  a  body 
would  thus  afford  the  means  of  fixing  its  atomic  wciyht. 
There  can  be  no  doubt  of  the  truth   of  this  in  numerous 
cases,  but  experiments  are  still  wanting  to  show  it  to  be 
universally  true.     Compound  atoms  have  in  some  cases  been 
shown  to  have  the  same  relations  to  heat  as  the   simple. 
This  is  true  of  many  of  the  carbonates,  and  some  sulphates. 

Isomorphism  and  Dimorphism. 

262.  Isomorphism  is  identity  of  crystalline  form,  with 
a  difference  of  chemical  constitution.     Identity  of  crystal- 
line form  was  formerly  supposed  to  indicate  an   identity  of 
chemical    composition.     We  now  know   that  certain  sub- 
stances may  replace  each  other  in  the  constitution  of  com- 
pounds,   without    changing   their   crystalline    form.     This 
property  is  called  isomorphism,  and  those  basis  which  admit 
of  mutual  substitution  are  termed  isomorphous.     Chemistry 

Who  first  observed  these  relations  ?  2GO.  What  are  atomic  volumes? 
261.  What  of  specific  heat  of  atoms  ?  262.  What  is  isomorphism  ? 
Give  examples. 


ISOMORPHISM   AND   DIMORPHISM.  163 

furnishes  us  many  examples  of  these  isomorphous  bodies. 
Thus,  alumina  and  peroxyd  of  iron  replace  each  other  in- 
definitely. The  carbonate  of  iron  and  carbonates  of  lime, 
magnesia,  and  manganese,  are  also  examples,  as  the  common 
sparry  iron,  (spathic  iron,}  which  is  a  carbonate  of  iron,  in 
which  a  large  portion  of  carbonate  of  lime  sometimes  exists 
without  producing  any  change  of  form  in  the  mineral.  Oxyd 
of  zinc  and  of  magnesia,  oxyd  of  copper,  and  protoxyd  of 
iron,  also  take  the  place  each  of  the  other  in  compounds, 
without  any  alteration  of  crystalline  form.  When  those 
bodies  unite  with  acids  to  form  salts,  the  resulting  com- 
pounds have  the  same  crystalline  form,  and,  if  they  have  the 
same  color,  are  not  to  be  distinguished  from  each  other  by 
the  eye. 

In  double  salts,  like  common  alum,  these  relations  are 
also  found.  Sulphate  of  iron  may  take  the  place  of  sul- 
phate of  alumina  in  common  alum,  and  no  change  of  form 
will  occur ;  and  soda  may,  in  like  manner,  replace  the  pot- 
ash. In  fact,  all  the  similar  compounds  of  isomorphous 
bodies  have  a  great  resemblance  to  each  other  in  general 
appearance  and  chemical  properties.  The  two  bases  in  a 
double  salt  are,  however,  never  taken  from  the  same  group 
of  isomorphous  bodies. 

263.  A  knowledge  of  this  law  is  of  great  importance  to 
the  chemist,  and  often  enables  him  to  explain,  in   a  satis- 
factory manner,  apparent  contradictions  and  anomalies,  and 
to  decide  many  doubtful  points.     It  is  supposed  that  the 
elements  whose  compounds  are  isomorphous,  are  themselves 
isomorphous. 

The  following  group  of  isomorphous  bodies  is  given  by 
Professor  Graham  in  his  "  Elements."  1st  family  :  Chlo- 
rine, Iodine,  Bromine,  Fluorine.  2d  family :  Sulphur, 
Selenium,  Tellurium.  3d  family :  Phosphorus,  Arsenic, 
Antimony.  4th  family  :  Barium,  Strontium,  Lead.  5th 
family  :  Silver,  Sodium,  Potassium,  Ammonium.  6th  fami- 
ly :  Magnesium,  Manganese,  Iron,  Cobalt,  Nickel,  Zinc, 
Copper,  Cadmium,  Aluminum,  Chromium,  Calcium,  Hy- 
drogen. 

264.  Dimorphism  and  Polymorphism. — Some  substances 
have  two  forms,  under  both  of  which  they  are  found.     Thus, 

In  what  double  salts  is  it  found  ?  263.  What  does  this  law  explain  ? 
What  groups  are  given  ?  261.  What  are  dimorphism  and  polymorphism  ? 


164  ELEMENTS — LAWS   OF   COMBINATION. 

common  calc-spar  (carbonate  of  lime)  generally  occurs  in 
rhombohedrons,  (49,  fig.  13,)  but  in  arragonite  (which  is  only 
pure  carbonate  of  lime)  it  is  seen  as  a  rhombic  prism, 
(46,  fig.  37.) 

Bin-iodid  of  mercury  is  another  example  of  the  same 
kind;  and  in  both  these  cases  the  change  of  form  is  effected 
by  heat.  Polymorphism  is  where  more  than  two  forms  of 
the  same  substance  are  known;  as  in  titanic  acid,  of  which 
rutile,  anatase,  andbrookite  are  three  distinct  cry  stallographic 
species. 

Chemical  Affinity. 

265.  Chemical    affinity,   or   the   capability   of  chemical 
union  between  bodies,  is  not  possessed  alike  by  all.  Oyxgen 
is  the  only  element  capable  of  forming  chemical  compounds 
with  all  other  elements.     Carbon  can  unite  with  oxygen, 
sulphur,   hydrogen,  and  some  other  bodies,  but  no  com- 
pound has  been  formed  between  it  and  gold,  silver,  fluorine, 
aluminum,  iodine,  and  bromine.     It  is,  therefore,  said  to 
have  no  affinity  for  those  bodies,  or  no  capability  of  union 
with  them.     The  power  of  union  among  bodies,  or  affinity, 
is  exceedingly  different  in  degree,  and  is  much  affected  by 
many  circumstances.     Thus  A  may  unite  with  B,  forming 
AB ;  but  if  C  had  been  present,  A  might  have  so  much 
more  affinity  for  C  than  it  has  for  B,  as   to  unite  with   it, 
forming  AC,  while  B  would  remain   unaffected.     For  ex- 
ample, sulphuric  acid  and  soda  unite  to  form  Glauber's  salts, 
or  sulphate  of  soda;  but  if  soda  and  baryta  had  both  been 
present,  and  sulphuric  acid  were  added,  only  the  sulphate 
^f  baryta  would  be  formed,  and  the  soda  would  remain  dis- 
engaged, unless  there  was  sulphuric  acid  enough  to  satisfy 
both.     This  is  what  is  sometimes  called  elective  affinity,  as 
if  the  acid  selected  the  baryta  rather  than  the  soda. 

266.  The  more  unlike,  as  a  general  thing,  any  two  bodies 
are  in  chemical  properties,  the  stronger  is  their  disposition 
to  unite.     The  metals,  as  a  class,  have  very  little  disposition 
to  unite  with  each   other.     But  they  unite  with  oxygen, 
chlorine,  and  sulphur,  forming  fixed  and  determinate  com- 
pounds.    The  alkalies,  potash   and   soda,  form  no  proper 

265.  What  of  chemical  affinity  ?  What  of  oxygen  ?  What  of  carbon  ? 
What  determines  the  union  of  A  o.nd  B?  How  if  C  were  present? 
What  is  this  sort  of  affinity  called  ?  266.  What  of  the  similarity  of 
bodies  ?  Illustrate  by  an  example. 


CHEMICAL   AFFINITY.  165 

compound  with  each  other,  and  their  alkaline  properties  aro 
not  altered  by  such  union.  Sulphuric  and  nitric  acid  may 
be  mingled  in  any  proportion,  but  no  new  compound  is 
formed,  and  the  mixture  is  still  acid.  But  if  the  potash 
and  soda  respectively  be  added  to  nitric  and  sulphuric  acid, 
the  result  will  be  saltpetre,  or  nitrate  of  potash,  and  Glau- 
ber's salts,  or  sulphate  of  soda,  two  salts  having  neither 
alkaline  nor  acid  properties. 

267.  Solution  is  the  result  of  a  feeble  affinity,  but  one  in 
which  the  properties  of  the  dissolved  body  are  unaltered : 
thus,  sugar  is  dissolved  in  all  proportions  in  water  or  weak 
alcohol.     Camphor  is  soluble  in  alcohol,  but  the  addition 
of  water  to  the  solution  will,  by  engaging  the  alcohol,  cause 
the  camphor  to  be  thrown  down.     Gum  is  soluble  in  water, 
but  not  in  alcohol.     We  have  already  seen  that  the  solu- 
tion of  various  salts  in  water  would  produce  cold  (124)  from 
the  change  of  state  in  the  body  dissolved. 

268.  The   circumstances   which    modify   the   action    of 
affinity  are  numerous,  some  of  which  we  may  briefly  notice. 
We  have  said  (8)  that  chemical  affinity  existed  only  among 
unlike  particles,  and  at  insensible  distances.     Intimate  con- 
tact among  particles  is,  therefore,  in  the  highest  degree 
necessary  to  promote  chemical  union.     Any  circumstance 
which  favors  such  contact  will  increase  the  activity  of,  or 
disposition  to,  chemical  combination.     Solution  brings  par- 
ticles near  together,  and  leaves  them  free  to  move  among 
each  other :  substances  in  a  state  of  solution  have,  there- 
fore, an  opportunity  to  unite,  which  they  do  not  possess 
when  solid.     Hence  the  old  maxim,  "  Corpora  non  agunt 
nisi  siut  soluta."     Carbonate  of  soda  and  tartaric  acid,  for 
example,  both  in  a  dry  state,  remain  unchanged ;  but  the 
addition  of  water  will  at  once,  by  dissolving  them,  bring 
about  a  union.     Heat  being,  in  fact,  a  most  powerful  means 
of  solution ;  will  often  cause  union  to  take  place.     Sand  or 
silica  will  not  unite  with  soda  or  potash  by  contact  or  aque- 
ous solution,  but  if  the  mixture  in  proper  proportions  is 
strongly  heated,  union  takes  place  and  glass  is  formed. 
Sulphur  will  not  unite  with  cold  iron,  but  if  the  iron  be 
heated  to  rednesss,  or  the  sulphur  melted,  a  vigorous  union 
takes  place,  and  a  sulphuret  of  iron  results.     Cohesion  is 
destroyed   by  heat  and   solution,   and    substances   in  fine 

267.  What  of  solution?     268.  Name  circumstances  affecting  affinity. 


166  ELEMENTS — LAWS   OF   COMBINATION". 

powder  unite  more  readily  than  in  masses  of  large  size. 
Dry  sal-ammoniac  and  dry  lime,  in  fine  powder,  mingled 
together,  evolve  ammonia.  This  is  an  interesting  example 
of  chemical  action,  by  mere  contact  of  dry  substances. 

269.  Bodies  in  the  nascent*  state  (as  it  is  called)  will 
often  unite,  when  under  ordinary  circumstances  no  affinity 
is  seen  between  them.     Thus  hydrogen  and  nitrogen  gases, 
under  ordinary  circumstances,  do  not  unite  if  mingled  in  the 
Bame  vessel ;  but  when  these  two  gases  are  set  free  at  the 
same  time,  from  the  decomposition  of  some  organic  matter, 
they  readily  unite,  forming  ammonia.     The  same  is  true  of 
carbon  under  the  same  circumstances,  which  will  then  unite 
in  a  great  variety  of  proportions  with  hydrogen  and  nitrogen, 
although  no  such  union  can  be  effected  among  these  bodies 
under  ordinary  circumstances. 

270.  The  quantity  of  matter,  as  well  as  the  order  and 
condition  in  which  substances  may  be  presented  to  each 
other,  often  exerts  an  important  influence  on  the  power  of 
affinity.    Thus,  vapor  of  water,  when  passed  through  a  gun- 
barrel  heated  to  redness,  will  be  decomposed,  the  oxygen 
uniting  with  the  iron,  while  the  hydrogen  escapes  at  the 
other  end  of  the  tube.     On  the  contrary,  if  dry  hydrogen  is 
passed  over  oxyd  of  iron  in  a  tube  heated  to  redness,  the 
hydrogen  unites  with  the  oxygen  of  the  oxyd  of  iron,  leav- 
ing metallic  iron,  while  vapor  of  water  escapes  at  the  open 
end  of  the  tube.     Other  examples  of  this  sort  are  observed, 
where  the  play  of  affinities  seems  to  be  determined  by  the 
preponderance  of  one  sort  of  matter  over  another,  or  by  the 
peculiar  condition  of  the  resulting  compounds,  as  regards 
insolubility,  or  the  power  of  vaporization. 

271.  The  presence  of  a  third  body  often  causes  a  union, 
or  the  exertion  of  the  force  of  affinity,  when  this  third  body 
takes  no  part  in  the  changes  which  happen.     Thus,  oxygen 
and  hydrogen  gases  may  be  mingled  without  any  combina- 
tion taking  place  between  them,  although  a  strong  affinity 
exists.     If,  however,  a  portion  of  platinum  in  a  state  of 
very  fine  division  (spongy  platinum)  be  introduced  into  the 
mixture,   union   takes  place,  sometimes  slowly,  but  more 

269.  What  of  the  nascent  state  ?     Give  an  example.     270.  What  of 
quantity  of  matter  ?     What  is  catalysis  ?     Give  examples. 

*  From  nascens,  being  born,  or  in  the  moment  of  formation. 


CHEMICAL   AFFINITY.  167 

often  with  an  explosion,  the  platinum  being  at  the  same 
time  heated  to  redness  from  the  rapid  condensation  of  the 
gases  which  takes  place  in  its  pores.  Advantage  is  taken 
of  this  fact  in  constructing  the  common  instrument  for 
lighting  tapers  by  a  stream  of  hydrogen  falling  on  spongy 
platinum.  No  change  is  suffered  in  this  case  by  the  plati- 
num, which  seems  to  act  by  its  presence  only.  Berzelius 
has  proposed  the  term  catalysis,  from  the  Greek  kata,  by, 
and  luo,  to  loosen,  to  express  the  peculiar  power  which 
some  bodies  possess  of  aiding  chemical  changes  by  their 
presence  merely. 


168 


PART  III.— INORGANIC  CHEMISTRY. 


CLASSIFICATION  OF  ELEMENTS. 

272.  It  is  usual  to  divide  elementary  bodies  into  two  great 
groups,  the  non-metallic  and  metallic  elements.  This  con- 
venient arrangement  is  founded  on  characters  which  in  a 
general  and  popular  sense  are  correct  and  easily  distinguished, 
but  which  fail  in  several  cases  to  afford  any  accurate  distinc- 
tion. No  one  can  doubt  to  which  class,  for  example,  gold 
and  sulphur  should  be  respectively  referred;  but  it  is  im- 
possible to  say  why  carbon  and  silicon  are  not  as  well  entitled 
to  be  classed  in  the  same  group  with  the  metals  as  tellurium 
and  arsenic,  if  we  except  the  single  character  of  lustre. 

We  will  discuss  the  first  division  of  elementary  bodies  in 
six  classes,  in  the  following  order : — 

f"|     The  only  element  which  forms  compounds 
1.  Oxygen I  with  all  others,  and  the  type  of  electro-ne- 
J  gativc  bodies. 

"I  Four  elements  very  similar  in  all  their 
sensible  properties,  forming  similar  com- 
pounds with  the  metals,  whose  acid  com- 
pounds with  oxygen  are  also  similar,  and 
have  the  constitution  expressed  by  HO, 
R04,  HO,,  ROV 

Those  stand  in  close  relation  with  each 
other,  while  their  compounds  with  the  me- 
tals are  more  similar  to  the  oxyds  of  those 
metals  than  are  the  analogous  compounds 
of  the  second  class.  Their  oxygen  acids 
have  the  formula  R0a,  R0». 

This  group  properly  includes  also  arsenic 
and  antimony,  which  are,  however,  from 
convenience,  discussed  elsewhere.  The 
four  form  similar  compounds  with  oxygen, 
RO,  R03,  R0§,  and  peculiar  gaseous  com- 
pounds with  hydrogen,  RII,. 
.. .  r  .  These  three  bodies  are  similar,  non-vola- 

To    e*r Uile,  combustible  bases,  and  alike  in  form- 

12.  bihcon hng  feeble  acids  with,  oxygen.    The  formula 

on J.ROais  adopted  by  some  chemists. 

~\      This  highly  electro-positive  body  is  un- 
14.  Hydrogen.     >  like  any  of  the  preceding,  and  has  analogies 
J  with  the  succeeding  group  of  metals. 


CLASS  ir. 


CLASS  in. 


CLASS  iv. 


CLASS  v. 


CLASS  vi. 


2.  Chlorine.... 

3.  Bromine.... 

4.  Iodine 

5.  Fluorine.... 


6.  Sulphur.... 

7.  Selenium.. 

8.  Tellurium. 


9.  Nitrogen 

10.  Phosphorus , 


272.  How  are  the  elements  divided?  What  of  the  accuracy  of  this 
division?  How  many  classes  are  named  for  1st  division?  Name  the 
1st  class,  the  2d,  the  3d,  the  4th.  What  other  elements  belong  to  this 
group?  What  is  the  formula  of  the  hydrogen  compounds  of  this  group  ? 
What  is  class  3  ?  Class  6  ? 


OXFGEN.  160 

273  We  will  consider  these  several  classes  separately. 
The  compounds  which  each  element  forms  with  those  before 
it,  will  be  taken  up  in  order ;  and  we  shall  then  be  better 
able  to  understand  the  relation  of  each  element  to  its  asso- 
ciates in  the  same  group.  The  several  classes,  too,  will  then 
be  better  understood  in  the  analogies  which  unite,  and  the 
differences  which  separate  them. 

CLASS  I. 

OXYGEN. 

Equivalent,  8.     Symbol,  0.     Density,  1-106. 

274.  Dr.  Priestley  discovered  oxygen  in  1774.     It  was 
also  rediscovered  by  Scheele,  of  Sweden,  immediately  after, 
and  without  a  knowledge  Of  Priestley's  discovery.     Before 
this  time,  all  gaseous  bodies  were  considered  to  be  only  modes 
of  common  air,  and  oxygen  was  first  called  vital  air,  and, 
in  allusion  to  the  then  existing  theories,  dephlogi&ticated 
air.     It  was  the  illustrious  Lavoisier,  author  of  the  present 
nomenclature  of  chemistry,  who  proposed  the  name  oxygen, 
(from  oxus,  acid,  and  gennao,  I  form.)     Lavoisier  had  also 
rediscovered  oxygen  in  1775.    At  that  time  it  was  supposed 
that  all  acids  contained  oxygen. 

Oxygen  is  the  most  widely  diffused  and  important  of  the 
elements.  It  forms  over  one-fifth  part  of  the  atmosphere 
by  weight,  eight-ninths  of  the  waters  of  the  globe,  and  pro- 
bably one-third  part  of  its  solid  crust.  It  has  also  the  widest 
range  of  affinities  of  all  known  substances,  and  by  its  im- 
mediate agency  combustion  and  life  are  alone  sustained. 

275.  Preparation. — Oxygen  gas  is  procured  by  heating 
the  oxyds  of  lead,  mercury,  or  of  manganese,  or  the  salts, 
nitrate  of  potassa,  chlorate  of  potassa,  or  nitrate  of  soda. 
Chlorate  of  potassa   is,   however,  the   salt   generally   em- 
ployed, as  yielding  a  large  volume  of  pure  oxygen  with  a 
gentle  heat.     This  salt  contains  six  equivalents  of  oxygen, 
and  parts  with  them  all  at  a  moderate  heat,  leaving  a  residue 
of  chlorid  of  potassium.     Thus  C105KO  =  ClK-f  60-    One 
ounce  of  chlorate  of  potassa  yields  543  cubic  inches  of  pure 
oxygen,  or  over  a  gallon  and  a  half.     The  arrangement  of 

273.  In  what  order  are  they  discussed  ?  274.  Who  discovered  oxygon, 
and  when  ?  How  were  gases  formerly  considered  ?  Who  named  oxygen  ? 
Whence  the  name  ?  What  of  the  importance  and  diffusion  of  oxygen  ? 
275.  How  is  it  prepared  ? 


170 


NON-METALLIC   ELEMENTS. 


apparatus  for  this  purpose  is  shown  in  fig.  206.  A  con- 
venient portion  of  chlorate  of  potassa  is  pulverized  and  mixed 

with  its  own  weight  of 
manganese,  or  better 
with  the  black  oxyd 
of  copper.  The  dry 
mixture  is  placed  in 
the  flask  a  of  hard 
glass,  where  it  is 
heated  by  the  lamp 
below.  A  bent  tube 
fitted  to  a  by  a  cork, 
conveys  the  gas  to  the 
air-bell  6,  previously 

Fig.  206.  filled  with  water  and 

inverted  in  the  water-trough.  The  heat  of  the  lamp  decom- 
poses the  salt,  and  pure  oxygen  is  freely  given  off,  displacing 
the  water  in  the  air-jar.  By  aid  of  the  oxyds  of  manganese 
or  copper  the  decomposition  of  the  chlorate  of  potassa  is 
rendered  gradual  and  safe.  Without  this  precaution  the 
operation  proceeds  with  almost  ungovernable  energy;  the 
whole  volume  of  gas  being  given  off  almost  at  the  same  instant, 
when  the  point  of  decomposition  is  reached.  The  metallic 
oxyd  seems  to  act  by  distributing  the  heat,  and  by  the  me- 
chanical distribution  of  the  salt:  clean  sand  may  be  used 
•with  nearly  equal  success.  The  glass  may  be  protected  from 
fusion  by  a  thin  metallic  cup  c  employed  as  a  sand-bath. 

276.  When  large 
volumes  of  oxygen 
gas  are  required,  a 
more  economical 
plan  is  to  heat  the 
peroxyd  of  man- 
ganese strongly  in 
an  iron  retort  ar- 
ranged in  a  rever- 
beratory  furnace, 
(fig.  207.)  One 
pound  of  good oxyd 
t  207.  of  manganese  will 


Give  the  way  by  chlorate  of  potassium.     Why  is  oxyd  of  manganese 
used  ?     How  does  it  act?     276.  What  is  the  process  by  fig.  207  ? 


OXYGEN.  171 

E'eld  seven  gallons  of  oxygen,  with  some  carbonic  acid.  This 
st  is  removed  by  passing  the  gas  through  t^e  wash-bottle 
10  containing  solution  of  potash,  which  absorbs  carbonic  acid. 
In  this  process  Mn03  becomes  MnO-f-0;  about  twelve 
per  cent,  of  the  weight  of  oxyd  employed  being  obtained 
as  oxygen.  Oxygen  gas  may  also  be  procured  from  oxyd 
of  manganese  by  aid  of  strong  sulphuric  acid  and  a  moderate 
heat.  The  mixture  is  placed  in  a  balloon  d,  (fig.  208,)  and 
heat  applied. 
Sulphate  of 
manganese  is 
formed,  and 
half  the  quan- 
tity of  oxygen 
in  the  original 
oxyd,  or  one 
equivalent,  is 
given  off.  Car- 
bonic acid  is 
removed  by 
the  potash  so- 
lution in  w.  Bichromate  of  potash  may  be  substituted  for 
the  oxyd  of  manganese  in  this  case  with  good  results.  Both 
should  be  in  fine  powder. 

277.  Properties  and  Experiments. — Oxygen,  when  pure, 
is  a  transparent,  colorless  gas,  which  no  degree  of  cold  or 
pressure  has  ever  reduced  to  a  liquid  state.  It  is  a  < 
little  heavier  than  the  atmosphere,  its  density  being, 
compared  to  air,  as  1-1057  : 1-000.  One  hundred  cubic 
inches  of  the  dry  gas  weigh  34-19  grains.  It  is  without 
taste  or  smell.  It  is  very  slightly  dissolved  in  water, 
one  hundred  volumes  of  water  dissolving  only  about 
four  and  a  half  of  the  gas.  Its  most  remarkable  pro- 
perty is  the  energy  with  which  it  supports  combustion. 
Any  body  which  will  burn  in  common  air,  burns  with  . 
greatly  increased  splendor  in  oxygen  gas.  A  newly  | 
extinguished  candle  or  taper,  (fig.  209,)  which  has  the  i 
least  fire  on  the  wick,  will  instantly  be  rekindled  in  Q* 
oxygen,  and  burn  in  it  with  great  beauty.  A  quart  Fig^oo, 

How  is  gas  of  this  source  purified  ?  What  is  the  reaction  of  heat 
on  manganese  ?  How  is  0  procured  by  sulphuric  acid  as  in  fig.  208  ? 
277.  What  are  the  properties  of  0  ?  How  does  it  act  on.  combustibles? 


172 


NON-METALLIC    ELEMENTS. 


JL'ig.  210. 


of  this  gas  in  a  narrow-mouthed  bottle,  will 
easily  relight  a  candle  fifty  times.  A  bit  of 
charcoal  bark  (fig.  210)  with  only  a  spark  of 
ignition  on  it,  attached  to  a  wire  and  lowered 
into  a  jar  of  this  gas,  will  burn  with  intense 
brilliancy,  producing  carbonic  acid.  A  steel 
watch-spring  dipped  in  melted  sulphur  and  ig- 
nited, when  lowered  into  a  jar  of  pure  oxygen 
gas;  bursts  into  the  most  magnificent  combus- 
tion, (fig.  211.)  The  oxyd  of  iron 
which  is  formed  falls  down  in  burn- 
ing globules,  like  glowing  meteors, 
which  fuse  themselves  into  the  glazed 
surface  of  an  earthen  plate,  although 
covered  with  an  inch  of  water.  If, 
as  often  happens,  a  motion  of  the 
spring  throws  a  globule  of  this  fused 
oxyd  against  the  side  of  the  glass 
vessel,  it  melts  itself  into  the  sub- 
stance of  the  glass,  or,  if  that  is  thin, 
goes  through  it.  This  is  one  of  the 
most  brilliant  and  instructive  expe- 
riments in  chemistry.  If  the  ori- 
fice at  top  is  closed  air-tight,  and  water  is  poured  into  the 
plate,  we  shall  find,  as  the  experiment  proceeds,  that  the 
water  will  rise  in  the  jar  as  the  gas  is  consumed.  If  we 
could  collect  and  weigh  the  globules  of  oxyd  of  iron,  we 
should  find  in  them  an  increase  of  weight  equal  to  the 
weight  of  the  oxygen  consumed. 

If  the  watch-spring  or  wire  is  coiled 
into  a  helix,  as  in  fig.  212,  then  the  com- 
bustion proceeds  in  a  most  beautiful 
series  of  revolutions,  greatly  heightening 
the  splendor  of  the  experiment.  These 
experiments  should  be  conducted  in  a 
dark  room  to  have  the  full  effect  of  their 
brilliancy. 

If  the  flame  of  a  lamp,  (Fig.  213,)  is 
supplied  by  a  jet  of  oxygen,  the  tempe- 
rature of  combustion  is  so  much  elevated 


Fig.  211. 


Fig.  212. 


Explain  the  experiments  in  figs.  210,  211,  and  212. 


OXYGEN,  173 

that  a  platina  wire  may  be  fused  in  it.  We 
thus  imitate  the  oxyhydrogen  blow-pipe  to 
be  described  further  on,  (385.) 

278.  Oxygen,  when  inhaled,  affects  life  by 
quickening  the  circulation  of  the  blood,  and 
causing  an  excitement,  which,  if  continued, 

would  result  in  general  inflammatory  symp-  ^^JT  ~ ^ 
toms  and  death.  In  an  atmosphere  of  pure 
oxygen  we  would  live  too  fast,  exactly  as  combustion  is 
too  rapid  in  an  atmosphere  of  this  gas.  It  exerts,  how- 
ever, no  specific  poisonous  influence,  being,  when  used  in 
moderation,  altogether  salutary,  and  often  resorted  to,  to 
inflate  the  lungs  of  drowned  persons,  and  not  unfrequently 
with  the  most  beneficial  results.  The  blood  is  constantly 
brought  into  contact  with  the  air  in  the  lungs,  and  it  is 
the  oxygen  in  the  air  which  is  the  active  agent  in  render- 
ing it  fit  to  sustain  life.  Pure  oxygen  is  constantly  supplied 
to  the  atmosphere  by  the  processes  of  vegetable  life. 

279.  Ozone,  the  allotropic  or  double  condition  of  oxygen. 
When  a  stream  of  electrical  sparks  is  passed  through  a  tube 
in  which  a  current  of  dry  pure  oxygen  is  flowing,  the  gas 
assumes  new  properties.     The  same  result  is  obtained  also 
where  water  is  electrolysed,  (224,)  when  phosphorus  slowly 
consumes  in  a  globe  of  moist  air,  or  when  a  Leyden  battery 
is  discharged.     In  all  these  cases  there  is  a  peculiar  odor, 
perceived  also  after  a  powerful  discharge  of  electricity  from 
the  clouds.     Hence  the  name  ozone,  from  ozumi,  to  smell. 
However  this  result  may  be  obtained,  it  is  observed  that 
oxygen  in  this  condition,  or  air  containing  it,  presents  much 
more  powerful  oxydizing  powers  than  ordinary  oxygen.     It 
will  turn  strips  of  white  paper  dipped  in  protosulphate  of 
manganese  to  brown  from  the  production  of  peroxyd  of  man- 
ganese.    It  will  decolorize  solution  of  indigo  as  promptly 
as    nitric    acid,  and  it  bleaches  even  more  powerfully  than 
chlorine.     This  body,  Schonbeiu,  its  discoverer,  regards  now 
as  an  allotropic  condition  of  oxygen,  (as  suggested  by  Berze- 
lius.)     Its  presence  in  the  air  is  shown  by  the  discoloration 
of  papers  dipped  in  iodid  of  starch  solution.     It  has  been 
argued,  but  on  insufficient  grounds,  that  this  body  in  the 


278.  How  is  the  lamp  flame  affected  ?  How  does  it  act  on  life  ?  How 
on  the  blood  ?  279.  What  of  ozone  ?  How  obtained  ?  What  ita  cha- 
racters '{ 


174 


NON-METALLIC   ELEMENTS. 


Fig.  214. 


sir  was  a  miasmatic  agent.     A  few  words  will  be  in  place 
here,  upon  the 

Management  of  Gases. 

280.  Pneumatic  Troughs.  —  Gases  not  absorbed  by  water, 

are  always  collected  in 
a  vessel  of  water,  called 
a  pneumatic  trough. 
Figure  214  shows  a 
small  neat  one,  made 
of  glass,  proper  for  the 
lecture-table  ;  but,  for 
general  purposes,  they 
are  usually  made,  like 
the  one  below,  (fig. 
215,)  of  japanned  cop- 
per, of  tin  plate,  or  of 
wood,  to  hold  several 
gallons  of  water.  The 
essential  parts  are  the  well  W,  in  which  the  air-jars  are 

filled,  and  a  shelf  S, 
covered  with  about  an 
inch  of  water.  A 
groove  or  channel  d 
is  made  in  the  shelf,  to 
allow  the  end  of  the 
gas-pipe  to  dip  under 
the  air-jar.  If  nothing 
better  is  at  hand,  a 
common  wooden  tub  or 
water-pail,  with  a  per- 
forated shelf  and  invert- 
ed funnel,  will  answer  for  small  operations.  Learners  are 
sometimes  puzzled  to  tell  why  the  water  stands  in  an  air- 
jar  above  the  level  of  the  cistern.  A  moment's  thought, 
however,  on  the  principles  of  atmospheric  pressure  (27) 
already  explained,  will  make  this  clear.  We  must  remem- 
ber, too,  that  gases  are  only  light  fluids,  and  must  be  pour- 
ed upward  in  water,  by  the  same  laws  which  require  fluids 
heavier  than  air  to  be  poured  downward. 

281.  To  store  large  quantities  of  gases,  capacious  vessels 


215. 


280.  What  is  a  pneumatic  trough  ?     How  are  gases  managed  ? 
poured  ?     281.  How  are  they  stored  ? 


How 


OXYGEN. 


175 


of  copper  or  tinned  iron  are  used,  which  are  called  gas- 
holders. These  vessels  are  made  frequently  to  hold  30  to 
50  gallons.  The  simplest  form  is  that  of  a  large  air-jar,  pro- 
vided with  stopcocks  at  the  top  for  the  entrance  and  escape 
of  the  gas,  and  contained  in  an  exterior  cylindrical  vessel  of 

water.     A   more   con- 
venient gas-holder  for 

some  purposes  is  that 

contrived  by  Mr.Pepys, 

a  view  and  section  of 

which  are  shown  in  the 

annexed    figures,  (216 

and  217.)     It  is  a  tight 

cylinder  of  copper  or 

tin  g,  with  a  shallow 

pan  of  the  same  metal, 

supported  above  it  by 

Fig.  216.  several  props,   two    of          FiS-  217- 

which  are  tubes  with  stopcocks,  a  b.  Near  the  bottom  is 
a  large  orifice  o,  for  receiving  the  gas.  To  use  this  instru- 
ment, it  is  first  filled  with  water  by  closing  the  lower  orifice 
o  with  a  large  cork,  and  opening  all  the  upper  ones 
a  b  s.  Water  is  then  poured  into  the  shallow  pan  '  p, 
until  it  runs  out  at  s,  which  is  then  closed;  the  remain- 
der of  the  air  escapes  through  b',  when  it  is  full,  the 
cocks  a  b  are  shut,  and  the  lower  orifice  being  then  opened, 
the  water,  sustained  by  the  pressure  of  the  air,  cannot 
escape  except  as  it  is  driven  out  by  the  entrance  of  the  gas 
at  o,  from  which  it  runs  as  fast  as  the  gas  enters.  When 
used,  arrangements  must  be  made  to 
provide  for  the  water  driven  out  by  the 
gas  entering  at  o.  The  gas  is  obtained 
for  use  by  drawing  it  off  from  the  orifice 
s  or  b  at  the  same  time  that  the 
shallow  pan  p  is  full  of  water,  and  the 
cock  a  open.  The  tube  to  which 
this  cock  is  attached  goes  nearly  to  the 
bottom  of  the  vessel.  An  air-jar  is 
easily  filled  with  gas  from  the  holder 
by  placing  it  full  of  water  in  the  upper 


Fig.  218. 


Explain  figures  216  and  217.    How  is  gas  drawn  from  the  cas  holder? 
Explain  figure  218. 


176  NON-METALLIC   ELEMENTS. 

pan,  (see  fig.  218,)  over  the  orifice  b ;  on  turning  the  twc 
stopcocks  a  by  the  gas  issues  from  b  and  fills  the  jar,  while 
the  water  of  the  jar  runs  down  the  pipe  a  to  supply  the 
place  of  the  gas. 

In  collecting  gas,  the  precaution  should  never  bo  neglected 
of  first  allowing  all  the  atmospheric  air  to  escape  from  the 
vessels,  before  any  of  the  gas  is  saved  for  use. 

Bags  of  vulcanized  India-rubber  cloth  are  prepared  by 
the  instrument-makers  as  gas-holders,  which  can  be  used 
without  the  inconvenience  of  employing  water.  They  are 
filled  by  the  flexible  pipe  p  and  stop- 
cock c,  (fig.  219,)  which  also  serve  for 
the  exit  of  the  gas 

Gases  which  are  absorbed  by  water 
may  be  collected  over  mercury;  the 

high  price  of  mercury  makes,  however, 

F.  this  an  expensive  method ;  moreover, 

some  gases — as  chlorine,  for  instance — 
act  chemically  on  the  mercury.  "We  may  better  collect  the 
absorbable  gases  in  clean  dry  vessels,  by  displacement  of 
air,  as  is  explained  in  the  next  section. 

CLASS  II. 

CHLORINE. 

Equivalent,  35-50.     Symbol,  Cl.     Density,  244. 

282.  History  and  Preparation. — This  very  remarkable 
element  was  first  noticed  by  Scheele,  in  1774,  while  examin- 
ing the  action  of  chlorohydric  acid  on  peroxyd  of  manga- 
nese. For  a  long  time  it  was  believed  to  be  a  compound 
body.  It  was  called  chlorine  by  Davy,  who  established  its 
elementary  character. 

It  is  easily  obtained  from  chlorohydric  acid  HC1,  by  its 
action  upon  pulverized  oxyd  of  manganese,  in  an  apparatus 
similar  to  figure  220.  The  acid  is  poured  in  at  pleasure  by 
the  safety  tube  s,  after  the  manganese  has  been  made  into 
a  paste  with  the  first  portions.  The  heat  of  a  lamp  or  a 
pan  of  coals  evolves  the  gas  freely.  It  is  rapidly  absorbed 
by  cold  water;  but  if  the  vessels  are  filled  with  water  of 


What  of  India-rubber  bags  ?  What  of  absorbable  gases  ?  282.  When 
and  by  whom  was  chlorine  discovered  ?  How  is  it  obtained  ?  How  is  it 
collected  2 


CHLORINE. 


177 


Fig.  220.  Fig.  221. 

100°  to  150°  temperature,  it  is  collected  with  little  loss. 
Any  acid  vapors  are  washed  out  in  w.  A  strong  solution  of 
common  salt  (brine)  does  not  absorb  chlorine,  and  may  be 
usefully  employed  in  some  cases  to  collect  this  gas  in  a  small 
porcelain  or  other  trough.  Owing  to  its  great  weight,  it  may 
also  be  very  conveniently  collected  by  displacement  of  air 
in  dry  vessels,  using  an  apparatus  like  figure  221.  The  fluc- 
tuations of  the  air  are  prevented  by  a  bit  of  card-board  with 
a  slit  on  one  side,  and  the  greenish  color  of  the  gas  enables 
the  operator  to  see  when  the  vessel  is  full.  The  vessels 
must  have  glass  stoppers  or  covers  of  glass  ground  tight; 
in  such,  the  gas  may  be  preserved  at  pleasure.  The  opera- 
tion should  be  performed  in  a  well-ventilated  apartment, 
to  avoid  injury  from  the  corrosive  and  irritating  gas. 

283.  In  this  process  the  affinities  are  between  the  man- 
ganese, for  one  equivalent  of  the  chlorine  in  the  acid,  form- 
ing chlorid  of  manganese,  and  between  the  oxygen  of  the 
manganese  and  the  hydrogen  of  the  acid,  forming  water 
The  following  symbols  will  render  this  more  clear  :  we  take 
Mn02  and  2HC1,  and  obtain  MnCl,  2HO,  and  CI. 

How  by  figure  221  ?     What  precaution  is  advised  ?     283.    What   are 
the  affinities  in  this  process  ?     Give  the  equation. 

12 


178 


NON-METALLIC   ELEMENTS. 


I 


The  last  equivalent  of  chlorine,  having  nothing  to  detain 
it,  is  given  off. 

Pure  chlorine  is  also  easily  obtained  by  acting  on  one 
part  of  powdered  bichromate  of  potash,  in  a  small  retort, 
with  six  parts  of  strong  hydrochloric  acid.  A  gentle  lamp- 
heat  is  required  to  begin  the  process,  which  then  goes  on 
without  further  application  of  heat,  yielding  abundance  of 
gas. 

Dry  chlorine  is 
obtained  by  using 
an  apparatus,  figure 
222,  attached  to 
the  evolution  flask 
fig.  220  by  o'f  any 
acid  vapors  are 
washed  out  in  the 
bottle  10,  and  all 
moisture  is  removed 
by  the  chlorid  of 
Fig-  222.  calcium  tube  a  b,  the 

dry  gas  being  collected  by  displacement  in  /. 

284.  Properties. — Chlorine  is  a  greenish-yellow  gas, 
(whence  its  name,  from  cliloros,  green,)  with  a  powerful  and 
suffocating  odor.  It  is  wholly  irrespirable  and  poisonous. 
Even  when  much  diluted  with  air,  it  produces  the  most 
annoying  irritation  of  the  throat,  with  stricture  of  the 
chest,  and  a  severe  cough,  which  continues  for  hours,  with 
the  discharge  of  much  thick  mucus.  The 
attempt  to  breathe  the  undiluted  gas  would  be 
fatal ;  yet,  in  a  very  small  quantity,  and  dis- 
solved in  water,  it  is  used  with  benefit  by  pa- 
tients suffering  under  pulmonary  consumption. 
For  this  purpose  an  inhalation  apparatus  is 
used,  like  fig.  223.  The  mouth  is  applied  at 
o,  the  air  enters  at  a,  and,  passing  through  the 
dilute  solution,  becomes  more  or  less  charged 
with  chlorine.  Cold  water  recently  boiled  ab- 
sorbs about  twice  its  bulk  of  chlorine  gas, 
Fig.  223.  acquiring  its  color  and  characteristic  pro- 
perties. This  solution  is  much  used  in  the  laboratory  in 


How  is  it  obtained  dry  ?    284.  What  are  its  properties  ?    How  does  it 
affect  respiration  ?    How  is  it  safely  inhaled  ? 


CHLORINE.  179 

preference  to  the  gas.  It  should  be  preserved  in  a  blue 
bottle,  or  in  one  covered  by  black  paper,  to  avoid  decompo- 
sition, (228.)  The  moist  gas  exposed  to  a  cold  of  32°  yields 
beautiful  yellow  crystals,  which  are  a  definite  compound 
of  one  equivalent  of  chlorine  and  ten  of  water,  (C1,10HO.) 
If  these  crystals  are  hermetically  sealed 
up  in  a  glass  tube,  (fig.  224,)  they  will, 
on  melting,  exert  a  pressure  of  five  atmo- 
spheres, so  as  to  liquefy  a  portion  of  the 
gas,  which  is  distinctly  seen  as  a  yellow  FiS-  224- 
fluid,  of  density  1-33,  not  miscible  with  the  water  which  is 
present.  It  does  not  solidify  at  zero.  Chlorine  is  one  of 
the  heaviest  of  the  gases,  its  density  being  2-44,  and  100 
cubic  inches  weighing  76'5  grains. 

285.  Chlorine  solution  readily  dissolves  gold-leaf,  forming 
chlorid  of  gold  :  silver  solution  produces  in  it  a  dense  pre- 
cipitate of  chlorid  of  silver,  which  ammonia  re- 
dissolves.      A  rod  a,  (fig.  225,)  moistened  in 
ammonia  water,  and  held  over  chlorine  solution, 
produces  a  dense  cloud  of  chlorid  of  ammonium. 

A  crystal  of  green  vitriol  dropped  into  a  test- 
tube  containing  chlorine  water,  gives  a  dark  so- 
lution at  bottom  of  perchlorid  of  iron.  FiS-  225- 

286.  The  bleaching  power  of  chlorine  is  one  of  its  most 
remarkable  and  valuable  properties.     The  solution  of  chlo- 
rine immediately  discharges  the  color  of  calico  rags  or  of 
writing-ink.     The  moist  gas  does  the  same,  but  the  dry  gas 
does  not  bleach.     Chlorine  is  evolved  in  the  arts  from  a 
mixture   of  salt,   sulphuric  acid,   and  manganese,  for  the 
bleaching  of  paper  and  rags,  and  of  all  manner  of  cotton  or 
linen  stuifs.     It  does  not  bleach  woollens,  nor  printers'  ink, 
probably  because  of  its  indifference  to  carbon,  which  forms 
the  basis  of  printers'  ink.    The  bleaching  power  is  probably 
due  to  its  affinity  for  hydrogen. 

287.  Chlorine   spontaneously  inflames-  phosphorus,  and 
powdered  metallic  arsenic,  or  antimony,  forming  chlorids  of 
those  substances.     A  rag  or  bit  of  paper,  wet  with  oil  of 
turpentine  and  held  in  a  bottle  of  chlorine,  is  inflamed,  and 

What  of  its  solution?  How  crystallized?  How  liquefied?  How 
dense?  285.  What  are  tests  for  chlorine?  286.  What  valuable  pro- 
perty of  Cl  is  named  ?  How  if  dry  gas  is  used  ?  How  is  it  evolved  in 
the  arts  ?  What  exceptions  to  its  bleaching  ?  Whence  this  property  ? 
287.  How  does  Cl  act  on  phosphorus,  <fcc.  ?  How  on  cils  ? 


180  NON-METALLIC   ELEMENTS. 

^          the  interior  of  the  vessel  is  coated  with  a  bril- 
*"  j         liant  black  varnisli  of  carbon,  derived  from  the 
oil.     A  candle  lowered  into  a  vessel  of  chlorine, 
(h'g.  220,)  is  slowly  extinguished,  with  the  escape 
of  a  dense  volume   of  smoke.     In  these  cases, 
the  action  is  between  the  chlorine  and  the  hydro- 
gen of  the  organic  substances.     The  disinfection 
of  offensive  apartments,  sewers,  and   other  like 
g*  22°*    places,  is  rapidly  accomplished  by  chlorine  and 
the  "  bleaching  powders." 

288.  DouUe   Condition,  or  AUotropi&m   of  Chlorine. — 
Chlorine   exists    both   in  an   active    and    a   passive    state. 
The  first  is  its  condition  as  ordinarily  known,  when  pre- 
pared  in    daylight.      If  an    aqueous    solution   of   chlorine 
be  prepared  as  before  mentioned,  in  recently  boiled  water, 
and  a  part   of  it   be  exposed  in  an  inverted  bulb  to  the 
direct  rays  of  the  sun,  or  a  strong  daylight,  while  another 
portion,  as  soon  as  prepared,  without  exposure  to  light,  is 
set  aside  in  a  dark  closet,  and  in  a  similar  vessel,  we  shall 
find  them  very  differently  affected.     That  which  was  in  the 

dark  will  have  undergone  no  change,  while  that  in 
the  sunlight  will  have  suffered  decomposition  ;  a 
notable  quantity  of  nearly  pure  oxygen  will  have 
collected  in  the  bulb,  as  shown  in  fig.  227,  and 
chlorohydric  acid  will  have  been  formed  in  the  fluid, 
from  the  union  of  the  chlorine  and  the  hydrogen  of 
the  water,  whose  oxygen  is  set  free.  The  rapidity 
Fig.  227.  Of  this  decomposition  of  water  by  the  chlorine,  de- 
pends on  the  intensity  of  the  sun's  rays,  and  the  tempera- 
ture, and  being  once  begun,  it  continues  afterward  even  in 
the  dark.  The  indigo  rays  (76)  are  chiefly  instrumental  in 
producing  this  effect.  (Draper.) 

Compounds  of  Chlorine  with  Oxygen. 

289.  Chlorine  and  oxygen  have  no  disposition  to  unite, 
under   any  circumstances,    directly;    but   numerous   com- 
pounds of  these  two  elements  are  produced  indirectly,  of 
which  we  tabulate  five,  as  follows  : — 


How  on  a  candle  ?  Whence  this  peculiarity?  What  of  disinfection  ? 
288.  How  does  light  affect  chlorine  ?  Illustrate  by  lig.  227.  What  raj 
effects  this  ? 


CHLORINE.  181 

Symbol. 

Hypochbrous  acid CIO 

Chlorous  acid C10a 

Hypochlorio  acid,  (peroxyd  of  chlorine,) C104 

Chloric  acid CIO, 

Hypcrchloric  acid , CIO, 

As  the  most  simple  method,  we  commence  with — 

290.  Chloric  Acid,  (C105). — This  most  important  com- 
pound of  chlorine  and  oxygen  is  formed  when  a  current  of 
chlorine  is  passed  through  a  solution  of  potash,  to  saturation. 
On  evaporating  this  solution,  flat  tabular  crystals  of  a  white 
salt  are  gradually  formed,  which  are  chlorate  of  potassa, 
while  chlorid  of  potassium  remains  in  the  solution.     The 
reaction  is  between  6   equivalents  of  chlorine  arid   6   of 
potassa,  forming  5  of  chlorid  of  potassium  and  I  of  chlorate 
of  potassa;  thus,  6C1+ 6KO=5KCl-fKO,C105.     Chlorio 
acid  is  obtained  separate  with  some  difficulty,  by  decom- 
posing a  solution   of  chlorate  of   baryta  by   the  requisite 
amount  of  sulphuric   acid,  and  gradually  evaporating   the 
filtered  liquid  to  a  syrup.     In  this  state  its  affinity  for  all 
combustible  matter  is  so  great,  that  it  cannot  be  kept  in 
contact  with  any  substance  containing  carbon  or  hydrogen. 
Paper  moistened  by  it  takes  fire  as  it  is  dried.     The  chlo- 
rates are  recognized  by  their  powerful  action  on  combustible 
matter,    by  yielding  pure    oxygen    when    heated,  and   by 
giving   out   the   yellow   chlorous   acid  when   treated  with 
sulphuric  acid. 

291.  Ilypochlorous  Acid,  (CIO.) — This  acid  gas  is   ob- 
tained when  a  current  of  chlorine  traverses  a  ivca/c  solution 
of  potassa,  when,  if  cold,  no  chlorate  of  potassa  is  formed, 
but  a  solution  having  most  remarkable  bleaching  powers. 
It   contains   both    chlorid  of  potassium 

and  hypochlorite  of  potassa ;  thus,  m 
2KO+2C1==KO,C10+KCL  It  is  ob- 
tained also  by  the  agitation  of  chlorine 
with  red  oxyd  of  mercury,  or  better  by 
passing  dry  chlorine  over  red  oxyd  of 
mercury,  contained,  as  in  fig.  228,  in  a 
horizontal  tube  b,  (shown  only  in  part,) 
and  condensing  the  evolved  gas  CIO  in  Fig.  228. 

28'J.  Name  the  compounds  of  Cl  and  0.  What  are  their  formulas  ? 
290.  What  is  chloric  acid?  How  formed?  What  the  reaction?  What 
character  hna  chloric  acid?  What  of  its  salts?  291.  What  is  hypo- 
chlorous  acid  ?  How  obtained  ?  (jive  the  reaction.  Explain  its  produc- 
tion l>y  fig.  227. 


182 


NON-METALLIC    ELEMENTS. 


the  U  tube,  refrigerated  by  means  of  ico  and  salt  in  the 
outer  vessel.  Chlorid  of  mercury  is  formed,  and  oxyd 
of  chlorine  CIO.  Hypochlorous  acid  is  a  light-yellow 
gas,  much  resembling  chlorine;  condensed,  it  is  a  reddish- 
yellow  corrosive  liquid,  boiling  at  68°,  and  sparingly 
soluble  in  water.  The  vapor  detonates  with  a  hot  iron :  water 
absorbs  200  times  its  volume  of  it,  and  gains  a  beautiful 
yellow  color  and  powerful  bleaching  properties.  Its  aqueous 
solution  is  very  unstable,  being  decomposed  by  light,  and 
even  by  agitation  with  irregular  bodies,  as  broken  glass. 
Hypochlorous  acid  is  one  of  the  most  powerful  oxydizing 
agents  known,  raising  sulphur  and  phosphorus  to  their 
highest  state  of  oxydation — a  result  which  only  strong 
nitric  acid  can  accomplish.  It  is  formed  from  two  volumes 
of  chlorine  and  one  of  oxygen  condensed  into  two  volumes. 
Thus, 

2  volumes  of  chlorine  weigh 4-880 

1  "  oxygen       "     1-105 


5-985-5-2  =  2-992 

while  experiment  gives  us  2-977  for  the  density  of  this  sub- 
stance. The  ciichlorine  of  Davy  is  a  mixture  of  chlorine 
and  chloro-chlorous  acid,  and  not  a  protoxyd  of  chlorine,  as 
was  supposed.  It  is  obtained  when  chlorohydric  acid  acts 
on  chlorate  of  potassa,  is  a  greenish-yellow  gas,  darker  than 
chlorine,  of  a  very  pungent  and  persistent  odor.  It  explodes 
with  a  hot  iron. 

292.  Chlorous,  liy- 
pochloric,  and  per- 
chloric acids  are  all 
procured  from  the' 
decomposition  of 
chloric  acid.  When 
fused  chlorate  of 
potassa  is  acted  on 
by  sulphuric  acid, 
in  the  vessel  b,  (fig. 
229,)  a  very  explo- 
sive, yellow  gas 
Fig.  229.  collects  in  a.  Thia 


What  ore  its  characters?     What  is  its  volume,  constitution,  and  den- 
flity  ?     What  is  euchlorine?   What  of  chlorous  and  hyperchlorous  acids  ? 


BROMINE.  183 

experiment  demands  great  precautions  to  avoid  accident. 
The  vessel  b  may  be  secured  by  setting  it  into  an  outer 
vessel  of  warm  water.  The  gas  explodes  by  a  warm  iron,  by 
pressure,  and  sometimes  without  any  apparent  cause. 

293.  If  strong  sulphuric  acid  is  poured  upon  a  small 
quantity  of  crystals  of  chlorate  of  potash  in  a  wine  glass,  a 
violent  crackling  is  heard,  and  the  glass  is  soon  filled  with 
the  heavy  yellow  vapors  of  the  chlorous  acid  gas,  which  at 
once  inflame  a  rag  held  over  it  wet  with  turpentine,  with  a 
smart  explosion.     If  chlorate  of  potash  is  mixed  with  sugar, 
(both  separately  pulverized  and  mingled  with  caution,)  a  drop 
of  sulphuric  acid  will  inflame  the  mixture  with  a  brilliant  com- 
bustion.    Phosphorus  burns  spontaneously  in  chlorous  acid 
gas :  if  some  small  fragments  of  phosphorus  are  added  to  a 
glass  of  water  at  the  bottom  of  which  a  few  crystals  of 
chlorate  of  potash  have  been  placed,  (fig.  230,) 

and  sulphuric  acid  is  introduced  by  means  of  a 
long-tubed  funnel  to  the  bottom  of  the  vessel, 
the  salt  is  decomposed,  and  the  phosphorus 
flashes  under  water  in  the  chlorous  acid  which 
is  set  at  liberty.  Fig.  230. 

BROMINE. 
Equivalent,  80.     Symbol,  Br.     Density,  in  vapor,  5-39. 

294.  History. — This  element  was  discovered  in  1826,  by 
M.  Balard,  in  the  mother-liquor,  or  residue  of  the  evapora- 
tion of  sea-water,  and  by  him  named  from  its  offensive  odor, 
(bromos,  bad  odor.)     It  is  widely  diffused  in  nature,  exist- 
ing in  minute  quantities  in  combination  with  various  bases 
in  the  salt-water  of  the  ocean,  of  the  Dead  Sea,  and  of 
nearly  all  salt-springs.     It  is  also  found  in  a  few  minerals. 
The  salines  of  our  Western  States  are  many  of  them  rich 
in  bromids.      It  has  been  largely  prepared  at  Freeport, 
Pennsylvania,  on  the  Ohio,  for  use  in  pharmacy. 

295.  Bromine  is  a  dense  red  fluid,  exhaling  at  common 
temperatures  a  deep  reddish-brown  vapor.     It  is  one  of  the 
heaviest  non-metallic  fluids  known,  its  density  being  from 
2-97  to  3-187.     Sulphuric  acid  floats  on  its  surface,  and  is 


What  precaution  is  given  ?  293.  What  of  sulphuric  acid  on  chlorato 
of  potassa  ?  What  is  the  action  on  phosphorus  ?  294.  Give  the  history 
of  bromine.  Where  is  it  found  ?  295.  Give  its  characters. 


184  NON-METALLIC    ELEMENTS. 

used  to  prevent  its  evaporation.  At  zero  it  freezes  into  a 
brittle  solid.  It  boils  at  116-5°.  A  few  drops  in  a  large 
flask  will  fill  the  whole  vessel,  when  slightly  warmed,  with 
blood-red  vapors,  which  have  a  density  of  5-39.  It  is  a 
non-conductor  of  electricity,  and  Buffers  no  change  of  pro- 
perties from  heat  or  electricity.  It  dissolves  slightly  in 
water,  forming  a  bleaching  solution;  and  at  32°,  if  left  in 
contact  with  water,  it  forms  a  crystalline  hydrate  with  it,  of 
a  red  bronze  color,  analogous  to  the  hydrate  of  chlorine.  It 
is  a  corrosive  and  deadly  poison,  disorganizing  organic  struc- 
tures with  great  energy.  One  drop  on  the  beak  of  a  bird 
produced  instant  death.  It  has  even  been  used  for  suicide. 
Its  odor  resembles  chlorine,  but  is  more  offensive  and  per- 
sistent. It  has  bleaching  properties.  In  a  word,  bromine 
in  all  its  properties  and  combinations,  has  the  greatest  ana- 
logy to  chlorine,  but  is  less  energetic  in  its  affinities,  being 
displaced  by  chlorine  from  its  combinations. 

Bromine  acts  with  explosive  violence  on  phosphorus,  po- 
tassium, antimony,  and  other  similar  substances,  forming 
bromids. 

296.  Bromine  is  used  in  photography,  and  its  compounds 
also  in  medicine.     It  is  detected  in  the  mother-liquor  of 
salt-water    by   chlorine    gas,  or  solution  of  chlorine,  which 
sets  it  free,  when   it  is  recognized   by   its   peculiar   color. 
Ether  added  to  this  solution  takes  up  the  liberated  bromine 
on  agitation,  and  floats  on  the  surface  in  a  reddish-brown 
stratum.     It  is  prepared  in  the  arts  by  distilling  a  mixture 
of  bromid  of  sodium,  manganese,  and  dilute  sulphuric  acid, 
and  collecting  the  product  in  a  cold  receiver. 

Bromic  acid  BrO-  is  similar  in  all  its  reactions  to  chloric 
acid,  and  forms  salts  with  alkaline  bases,  called  bromates. 

The  chloride  of  bromine  BrCl5  is  soluble  in  water  and  de- 
composed by  alkalies. 

IODINE. 
Equivalent,  127.      Symbol,  I.     Density  in  vapor,  8*7. 

297.  History. — Like  chlorine  and  bromine,  this  substance 
has  its  origin  in  the  sea,  being  secreted  by  nearly  all  sea- 
weeds from  the  waters  of  the  ocean.     It  was  discovered  in 

What  smell  has  it  ?  How  does  it  act  on  combustibles  ?  296.  How 
used?  How  detected'  What  compounds  does  it  form  ?  297.  What  is 
ihc  history  of  iodine? 


IODINE.  185 

1811,  by  M.  Courtois,  of  Paris,  in  the  kelp,  or  ashes  of  sea- 
weeds. The  common  bladder  sea-weed,  (Jfucus  vesiculosus,') 
and  many  other  sea- weeds  of  our  own  coasts,  abound  in  salts 
of  iodine.  It  has  been  found  in  mineral  springs  associated 
with  bromine,  but  less  abundantly,  and  also  in  one  or  two 
minerals.  In  the  arts  its  chief  uses  are  for  the  photographic 
pictures,  and  in  the  process  of  dyeing.  In  medicine  it  is 
of  great  value,  in  glandular  and  other  diseases. 

298.  Preparation. — ^Kelp  is  treated  with  water,  which 
washes  out  all  the  soluble  salts,  and  the  filtered  solution  is 
evaporated  until  nearly  all  the  carbonate  of  soda  and  other 
saline  matters  have  crystallized  out.     The  remaining  liquor, 
which  contains  the  iodine,  as  iodid  of  magnesium,  &c.,  is 
mixed  with  successive  portions  of  sulphuric  acid  in  a  leaden 
retort,  and  after  standing  some  days  to  allow  the  sulphu- 
retted hydrogen,  &c.,  to  escape,  peroxyd  of  manganese  is 
added,  and  the  whole  gently  heated.     Iodine  distils  over  in 
a  purple  vapor,  and  is  condensed  in  a  receiver,  or  in  a  series 
of  two-necked  globes. 

299.  Properties. — Iodine  crystallizes  in  brilliant  blue- 
black  scales  of  a  metallic  lustre,  somewhat  resembling  plum- 
bago.    When  slowly  cooled  from  a  state  of  dense  vapor  in 
a  glass-tube  hermetically  sealed,  it  crystallizes  in  acute  octa- 
hedrons with  a  rhombic  base,  (46.)     The  density  of  iodine 
is  4-95,  it  melts  at  235°,  and  boils  at  247°,  forming  a  superb 
violet  vapor  of  unequalled  beauty;  (hence  its  name,  iodes,  like 
a  violet.)     For  this  purpose  a  few  grains  of  it  may  be  vola- 
tilized in  a  bolt-head,  or  from  a  hot  surface  under  a  bell,  as 

in  fig.  231,  when  on  cooling  it  is  deposited 
in  brilliant  crystals  lining  the  glass.  It 
assumes  the  sphreoidal  state  in  a  red-hot 
crucible,  forming  a  splendid  experiment, 
(131.)  It  is  almost  insoluble,  one  part  dis- 
solving in  7000  parts  of  water.  Alcohol 
dissolves  it  largely,  forming  tincture  of 
-  231  iodine.  Sal-ammoniac,  nitrate  of  ammonia, 
and  soluble  iodids  also  dissolve  it.  It  tem- 
porarily stains  the  skin  deep  brown,  and  its  odor  reminds  us 
somewhat  of  chlorine. 

300.  Chlorine  and  bromine  both  decompose   the  corn- 
In  what  is  it  found  ?     How  pTepared  ?     299.  What  are  its  characters? 

What  of  its  vapor  ?     How  soluble  ?      What  dissolves  it? 


186  NON-METALLIC   ELEMENTS. 

pounds  of  iodine.  Iodine  is  an  energetic  poison.  Iodine 
forms  a  beautiful  deep-blue  compound  with  a  cold  solution 
of  common  starch.  By  this  test  a  millionth  part  of  iodine 
can  be  detected.  In  combination  it  is  detected  by  the  same 
agent,  if  a  little  nitric  acid  or  chlorine  water  is  previously 
added  to  the  fluid  supposed  to  contain  an  iodid,  whereby 
the  iodine  is  set  free.  Acetate  of  lead  added  to  solutions  of 
salts  of  iodine  produces  a  yellow  crystalline  precipitate.  The 
iodid  of  potassium  is  the  salt  most  familiarly  known  of  all 
the  iodine  compounds,  and  is  the  usual  form  in  which  this 
substance  is  administered  medicinally. 

Compounds  of  Iodine  with  Oxygen. 

301.  Iodine  unites  with  oxygen,  forming  hypoiodic,  iodic, 
and  hi/periodic  acids.    Their  constitution  is  seen  in  the  fol- 
lowing formula) : 

Hypoiodic  acid I0t 

lodicacid 10. 

Hyperiodic  acid I0t 

These  acids  are  analogous  to  the  hypochloric,  chloric,  and 
perchloric  acids.  lodic  acid  is  formed  by  the  action  of 
strong  nitric  acid  on  iodine,  and  subsequent  evaporation,  to 
expel  the  free  nitric  acid  remaining.  It  is  a  very  soluble 
substance,  and  crystallizes  in  six-sided  tables.  Chlorine 
unites  with  iodine,  forming  two,  and  possibly  three  distinct 
chlorids,  (Id,  IC13,  and  IC15.)  These  are  formed  by  the 
direct  action  of  chlorine  on  dry  iodine.  There  are  also  bro- 
mids  of  iodine  of  uncertain  composition. 

FLUORINE. 
Equivalent,  19.  Symbol,  F.   Density,  (hypothetical,)  1-292 

302.  This  element  is  known  entirely  by  its  compounds 
Its  remarkable  energy  of  combination  with  other  elements, 
and  especially  with  silicon,  which  is  a  constituent  of  all 
glass,  has  rendered  its  isolation  very  difficult.     It  is  a  yel- 
lowish-brown gas,  having  the  smell  and  bleaching  proper- 
ties of  chlorine.     It  does  not  act  on  glass,  (as  its  compound 
with   hydrogen   does,)  but  unites  directly  with  gold.     Its 
specific  gravity  is  1-292. 

Fluorine  forms  no  compound  with  oxygen,  and  probably 

300.  Give  tests  for  iodine.  Give  its  oxygen  compounds?  S02.  What 
Crf  fluorine  ?  Why  is  it  difficult  to  isolate  ? 


SULPHUR.  187 

holds  a  place  intermediate  between  oxygen  and  chlorine. 
Its  most  remarkable  compound,  fluohydric  acid,  we  shall 
mention  in  the  section  on  hydrogen.  Its  power  of  etching 
glass  was  known  long  before  fluorine  was  suspected  to 
exist. 

303.  When  a  mixture  of  fluor-spar  with  peroxyd  of  man- 
ganese and  sulphuric  acid  is  heated,  a  reaction  takes  place, 
by  which  fluorine  in  an  impure  form  is  disengaged.     If  the 
gas  thus  produced  is  passed  through  water  having  iodine  sus- 
pended in  it,  combination  takes  place,  and  a  fluorid  of  iodine 
is  formed,  which  crystallizes  in  yellow  scales.     A  fluorid  of 
bromine  is  formed  by  a  similar  process,  which  has  been  used 
hvthe  photographic  art  with  success.    It  is  not  crystallizable. 
The  precise  composition  of  these  bodies  is  not  known 

The  atomic  weight  of  fluorine  is  very  nearly  an  aliquot 
part  of  the  equivalents  of  chlorine,  bromine,  and  iodine,  and 
these  four  bodies  form  a  well-marked  natural  family,  closely 
related  by  many  similar  properties. 

CLASS  III. 

SULPHUR. 
Equivalent,  16'0.    Symbol,  S.    Density  in  vapor,  6-654. 

304.  History. — Sulphur  is  one  of  those  elements  which, 
occurring  abundantly  in  nature,  have  been  known  from  the 
remotest  antiquity.     It  is  found  in  many  volcanic  regions, 
as  in  the  Island  of  Sicily,  the  vicinity  of  Naples,  in  Cuba, 
and  many  islands  of  the  Pacific.     Recent  volcanic  regions 
producing  sulphur  are  called  solfataras.     It  is  also  found 
in  beds  of  gypsum,  as  a  rock,  near  Cadiz  in  Spain,  and  at 
Cracow  in  Poland.     Sulphurets  of  iron,  copper,  and  other 
metals  are  widely  diffused  in  the  earth  •  and  in  combination 
as  sulphuric  acid,  sulphur  forms  nearly  half  of  the  weight 
of 'common  gypsum,  or  plaster  of  Paris. 

305.  Properties. — It  is  a  straw-yellow,  brittle  solid  at 
common    temperatures,   having  a  gravity  of  1-98.     It  is 
tasteless,  and  without  odor  until  rubbed.     By  warmth  and 
friction  it  acquires  its  well-known  brimstone  odor.     It  is  a 
non-conductor  of  heat  and  electricity.     By  friction  it  gives 

How  is  fluorine  disengaged  ?  What  of  its  atomic  weight  ?  304.  What 
is  the  history  of  sulphur  ?  305.  What  are  its  equivalent  and  characters  1 


188  NON-METALLIC   ELEMENTS. 

negative  electricity  abundantly.  It  is  very  volatile,  sublim- 
ing in  "flowers  of  sulphur" — minute  crystals — even  below 
the  melting  point,  or  226°.  By  this  means  it  is  freed  from 
earthy  and  other  impurities.  When  fused  below  280°  it  is 
an  amber-colored  mobile  fluid,  lighter  than  solid  sulphur, 
which  sinks  in  it.  It  is  cast  in  moulds,  giving  roll  sulphur. 
On  cooling,  it  shrinks  so  as  to  fall  from  the  mould,  (fig.  232.) 
The  roll  sulphur  held  for  a  moment  in  the  hand 
gives  a  peculiar  crackling  sound,  from  the  disturb- 
ance of  its  particles  by  heat,  and  it  often  breaks 
when  so  held.  It  is  insoluble  in  water,  and  nearly 
so  in  alcohol  and  ether.  In  oil  of  turpentine  and 
some  other  oils,  it  is  partly  soluble,  and  largely  so 
in  bisulphid  of  carbon.  Vapor  of  alcohol  also  dis- 
solves sulphur  vapor. 

Sulphur  is  very  combustible,  burning  with  a 
blue  flame  and  the  familiar  odor  of  a  match,  due 
to  the  production  of  sulphurous  add.  It  combines 
energetically  with  metals,  forming  sulphurets  or 
sulphids,  supporting  combustion  like  oxygen. 
Fig.  232.  Thus,  a  bundle  of  iron  wires,  as  shown  by  Dr.  Hare, 


Fig.  233.  Fig.  234.  Fig.  235. 

(fig.  233,)  is  rapidly  burned  with  scintillations,  when  held 
in  the  jet  of  sulphur  vapor  is.  uing  from  a  gun-barrel,  the 
end  of  which  has  been  heated  to  redness,  bits  of  roll  sul- 
phur thrown  in,  and  the  muzzle  stopped  with  a  cork. 

306.  Sulphur  occurs  in  two  distinct  crystalline  forms, 
one  of  which  is  the  right  rhombic  octohedron  and  the  other 
is  the  oblique  rhombic  prism.  Figures  234  and  235  give  its 
usual  form  as  found  in  nature  or  as  crystallizing  from  solution. 
When  slowly  cooled  from  fusion,  as  in  a  crucible,  if  the 
crust  formed  on  the  surface  be  pierced  while  the  interior  is 

How  is  it  purified  ?  How  does  heat  affect  it  ?  What  solubility  has  it  ? 
How  does  it  act  on  combustibles?  What  is  Hare's  experiment?  306. 
What  of  the  form  of  sulphur? 


SULPHUR.  189 

still  fluid,  and  the  liquid  part  turned  out, 
the  interior  will  present,  as  in  fig.  236, 
long,  slender,  compressed  prisms.  These 
belong  to  the  second  form  of  sulphur. 
This  was  one  of  the  first  instances  of 
dimorphism  noticed  by  Mitscherlich. 

307.  The  fusion  of  sulphur  at  different 
temperatures   presents  remarkable  facts. 
At  226°-280°  it  is   a   clear,  straw-yel- 
low fluid;   before  reaching  280°  it  begins  to  grow  darker  ; 
from  that  point  to  300°  it  assumes  a  deep  yellow  color;  at 
374°  it  has  an  orange  tint  and  becomes  somewhat  viscid ; 
at  500°  it  becomes  dull-brown,  and  at  this  high  temperature 
its  viscidity  is  such  that  the  vessel  containing  it  may  be 
turned  over  without  the  sulphur  falling  out.     Above  this 
last  temperature  it  begins  to  grow  more  fluid.     If  at  this 
moment  it  is  thrown  into  cold  water,  it  remains  pasty,  trans- 
parent, preserves  its  brown  color,  and  may  be  drawn  out 
into   long   threads   which    have    almost   the   elasticity  of 
caoutchouc.     It  regains  its  original  brittleness  only  after 
many  hours.     In  this  pasty  state,  sulphur  may  be  moulded 
by  the  hands,  and  is  used  to  copy  medallions  and  other 
works  of  art.     At  600°  it  is  volatilized  in  a  deep  red-brown 
vapor,  resembling  the  vapor  of  bromine.     The  density  of 
its  vapor  is  6-654. 

308.  In  its  chemical  relations,  sulphur  much  resembles 
oxygen.     It  forms  sulphurets  with  most  of  the  elements  that 
form  oxyds,  and  these  sulphurets  often  unite  to  form  bodies 
analogous  to  salts,  as  the  oxyds  do.     Berzelius  insists,  very 
properly,  that  its  binary  combinations,  from  their  analogy 
to  the  oxyds,  should  be  called  sulphids,  and  not  sulphurets. 

Its  uses  are  well  known.  It  is  one  of  the  essential  ingre- 
dients of  gunpowder,  and  is  the  basis  of  matches  of  all 
kinds.  Nearly  all  the  sulphuric  acid  used  in  the  arts  is 
made  from  it.  The  gas  arising  from  its  combustion  is  em- 
ployed in  bleaching  straw  and  woollen  goods ;  and  in  medi- 
cine it  has  a  specific  power  in  certain  obstinate  cutaneous 
diseases. 

The  flowers  of  sulphur  of  commerce  nearly  always  have  an 
acid  reaction,  due  to  the  sulphurous  acid  formed  in  sublima- 

H<rw  is  it  obtained  crystallized  ?  307.  Give  the  facts  observed  in  it* 
fusion.  What  of  its  vapor?  308.  What  are  tho  relations  of  sulphur? 
What  its  uses? 


190 


NON-METALLIC   ELEMENTS. 


tion.  All  the  sulphur  of  commerce  is  obtained  from  ils 
ores  by  sublimation  in  large  chambers, — or,  when  cast  in 
blocks,  by  distillation  and  fusion  in  earthenware  pots. 

Compounds  of  Sulphur  with  Oxygen. 

309.  The  compounds  of  sulphur  and  oxygen  are  nume- 
rous, but  only  two  of  them  will  engage  our  attention  at 
present,  namely: 

Sulphurous  acid SO* 

Sulphuric  acid S0» 

The  other  compounds  of  sulphur  and  oxygen  are   ex- 
pressed by  the  formula  Sa03,  SaO.>  S305,  S405>  S505. 

310.  Sulphurous  Acid,  S02. — Preparation. — This  is  the 
sole  product  of  the  combustion  of  sulphur  in  oxygen,  as  in 
the  experiment  figured  in  fig.  237,  where  burning  sulphur 


Fig.  237. 


Fig.  238. 


in  a  spoon  is  lowered  into  a  jar  of  oxygen  gas.  Other 
methods  are  used  however  in  the  laboratory  to  procure  this 
gas.  One  of  the  best  is  to  heat  in  a  retort  or  flask  (fig. 
238)  an  intimate  mixture  of  six  parts  of  peroxyd  of  manga- 
nese and  1  of  flowers  of  sulphur,  in  fine  powder.  The  sul- 
phur is  burned  at  the  expense  of  one  portion  of  the  oxygen 
of  the  peroxyd  of  manganese.  The  sulphurous  acid  gas 
is  given  off  abundantly,  and  may  be  freed  of  a  little  vo- 
latilized sulphur,  by  a  wash-bottle.  Mercury  and  copper 
also  decompose  sulphuric  acid,  yielding  sulphurous  acid,  by 
aid  of  heat ;  but  the  first  method  is  much  preferable  on 
every  account.  It  must  be  collected  in  dry  vessels  or  over 
mercury. 


309.  What  are  its  oxygen  compounds  ? 
prepared  in  fig.  237  ?     How  collected  ? 


510.  What  is  SO,?    How 


SULPHUR.  191 

311.  Properties. — Sulphurous  acid  is  a  colorless  acid  gas, 
with  a  pungent,  suffocating  odor,  recognized  as  that  of  a 
burning  match.     It  extinguishes  flame.     A  lighted  candle 
lowered  into  a  jar  containing  it  is  extinguished,  and  the 
edges  of  the  flame,  as  it  expires,  are  tinged  with  green. 

A  solution  of  blue  litmus  or  purple  cabbage  turned  into 
a  jar  of  the  gas  is  at  first  reddened  by  the  acid,  and  then 
bleached.  Articles  bleached  by  it,  after  a  time  regain  their 
previous  color.  Water  at  60°  absorbs  nearly  fifty  times  its 
volume  of  sulphurous  acid,  forming  a  strongly  acid  fluid. 
Hence  the  necessity  for  collecting  this  gas  over  mercury,  or 
by  displacement  of  air  in  dry  vessels.  Its  avidity  for  mois- 
ture is  so  great  that  it  forms  an  acid  fog  with  the  water  in 
the  atmosphere,  and  a  bit  of  ice  slipped  under  a  jar  of  it 
on  the  mercurial  cistern  is  instantly  melted;  the  water  ab- 
sorbs the  gas,  and  the  mercury  rises  to  fill  the  jar. 

312.  Sulphurous  acid  is  easily  liquefied  under  ordinary 
pressures  at  14°  and  below,  using  a  tube  with  a  bulb  E,  like 

fig.  239,  placed  in  a  refrigerating  vessel 
F.  The  gas  is  first  dried  by  chlorid  of 
calcium  before  passing  into  E.  The 
liquid  gas  is  easily  preserved  by  turn- 
ing it  into  a  tube  drawn  out  like  A  B, 
(fig.  240,)  and  previously  refrigerated. 
The  part  A  serves  for  a  funnel.  The 
blowpipe  flame  seals  it  hermetically  at 
or,  and  it  may  be  then  preserved  for 
future  use.  Under  a  pressure  of  two 
atmospheres,  this  gas  is  condensed  at  a  temperature  Fig-  240. 
of  59°.  It  is  a  colorless  mobile  fluid  of  a  density  of  1-42. 
Its  evaporation  produces  intense  cold.  If  the  ball  of  a 
mercury  thermometer  is  enveloped  in  cotton  and  moistened 
by  liquid  sulphurous  acid,  the  mercury  is  frozen,  and  a  spirit 
of  wine  thermometer  indicates  a  temperature  as  low  as 
—  60°.  By  its  evaporation  water  is  frozen  in  a  red-hot  cru- 
cible. It  is  a  crystalline  solid,  transparent  and  colorless,  at 
105°,  sinking  in  the  liquid  gas. 

313.  The  volume  of  sulphurous  acid  is  the  same  as  that 
of  the  oxygen  employed  in  producing  it.    In  other  words,  sul- 

311.  Give  its  properties.  What  of  its  bleaching?  Of  its  avidity  for 
moisture?  312.  How  and  at  what  temperature  liquefied  ?  How  collected 
and  preserved  ?  AVhat  of  its  sudden  evaporation  ?  What  temperature  ? 
313.  What  of  the  volume  of  SOj?  Give  the  calculation. 


192  NON-METALLIC    ELEMENTS. 

phurous  acid  contains  1  volume  of  oxygen  and  ^  voiume 
of  sulphur  vapor  (258)  condensed  into  1  volume.     Thus, 

One  volume  of  sulphurous  acid  density  ........................  2'247 

Substract  the  weight  of  1  volume  of  oxygen  .................  1*106 

Leaving  .................................................................  1*141 

Which  represents   very  nearly  Jth  volume   of  sulphur 


1-109 
6 

By  weight,  sulphurous  acid  contains  sulphur  50-87, 
oxygen  49-13=100.  One  hundred  cubic  inches  of  it 
weigh  68-70  grains. 

3  14.  Besides  its  use  in  bleaching  straw  and  woollen  goods, 
sulphurous  acid  is  employed  as  a  bath  for  diseases  of  the 
skin,  and  is  a  powerful  disinfectant,  even  arresting  putrefac- 
tion and  fermentation. 

Sulphites  are  salts  containing  sulphurous  acid.  Their 
solutions  are  gradually  changed  to  sulphates  by  absorbing 
oxygen. 

315.  Sulphuric  acid,  S03.HO.—  This  acid  is  one  of  the 
most  important  compounds  known;  its  affinities  are  very 
powerful,  and  no  class  of  bodies  is  better  understood  by 
chemists  than  the  sulphates.     In  the  arts  great  use  is  made 
of  sulphuric  acid,  many  millions  of  pounds  of  it  being  an- 
nually consumed   in    manufacturing   nitric   and   muriatic 
acids,  the  sulphates  of  copper  and  alum,  in  the  process  of 
dyeing,  and  more  than  all,  in  the  manufacture  of  carbonate 
of  soda  from  sea-salt. 

It  is  not  formed  by  the  direct  union  of  its  elements,  since 
we  have  seen  that  only  sulphurous  acid  can  result  from  the 
combustion  of  sulphur  in  oxygen.  Sulphurous  acid  must 
be  oxydized  to  form  sulphuric  acid. 

316.  This  may  be  done  by  passing  a  mixture  of  sulphur- 
ous acid  with  common  air  over  spongy  platinum,  heated  to 
redness  in  a  tube,  when  there  will  issue  from  the  open  end 
of  the  tube  a  mixture  of  sulphuric  acid  in  vapor,  with  ni- 
trogen from  the  air.     In  the  arts,  however,  this  process 
cannot  be  used  \  but  sulphuric  acid  is  made  on  a  large  scale 
by    bringing    together    sulphurous    acid    S03,    hyponitric 
acid  N04,  and  water  HO,  all  in  a  state  of  vapor,  in  a  large 
chamber,  or  series  of  chambers,  lined  with  lead,  when  sul- 


What  of  its  density  ?     314.  What  of  the  uses  of  sulphurous  acid  ?     31 5. 
What  of  SO,  ?    What  it?  use  ?     316.  How  is  SO,  formed  ? 


SULPHUR - 


193 


phmous  acid  S03  passes  to  a  higher  state  of  oxydation 
S03  at  the  expense  of  one-half  the  oxygen  of  the  hypo- 
nitric  acid  N04,  which  thus  becomes  reduced  to  the  state 
of  the  deutoxyd 
ofnitrogen,(N02-) 
The  arrangement 
employed  is  repre- 
sented in  fig.  241. 
A  A  is  a  chamber, 
fifty  feet  or  more 
long,  lined  on  all 
sides  with  sheet- 
lead.  A  very  large 
leaden  tube  B, 
opening  into  one 
end  of  the  cham- 

,  . 

ber,  communicates 
with  a  furnace.  Its  lower  end  rests  in  a  gutter  o  o  of 
dilute  acid,  to  prevent  the  effects  of  too  much  heat  and  the 
escape  of  the  vapors.  The  sulphur  is  introduced  by  a  door 
c  to  an  iron  pan;  and  a  fire  built  beneath,  n.  The  heat 
melts  the  sulphur,  which  burns  in  a  current  of  air  passing 
over  it,  and  the  sulphurous  acid  thus  formed  enters  the 
chamber,  in  company  with  air,  and  the  vapors  of  nitric  and 
hyponitric  acids  set  free  from  small  iron  pans  standing  over 
the  sulphur,  and  containing  the  materials  to  evolve  nitric  acid, 
(sulphuric  acid  and  saltpetre.)  A  small  steam-boiler  e 
furnishes  a  jet  of  steam  x  as  required,  and  a  quantity  of 
water  covers  the  floor,  which  is  inclined  so  as  to  be  deepest 
at  k.  A  chimney  with  a  valve  or  damper  p  allows  the 
escape  of  spent  and  useless  gases.  Things  being  thus  ar- 
ranged, the  chamber  receives  a  constant  supply  of  sulphur- 
ous acid,  common  air.  nitric  acid  vapor,  and  steam. 

317.  These  compounds  react  with  each  other  in  such  a 
manner  that  the  oxygen  of  the  air  is  constantly  transferred 
to  the  sulphurous  acid,  to  form  sulphuric  acid.  Deutoxyd 
of  nitrogen  N03  in  contact  with  air  becomes  hyponitric  acid 
N04,  and  this  last  in  presence  of  a  large  quantity  of  water  is 
transformed  into  nitric  acid  N05  and  deutoxyd  of  nitrogen. 
Thus,  GNO^HO^NO.+wHO-f-^NO,,.  Now,  sulphur- 
ous acid,  in  presence  of  hydrated  nitric  acid  (N05-(-wHO) 

Explain  the  fig.  241.  317.  Whence  the  oxygen  to  form  S0«  ?  Giv« 
the  reactions  by  the  formulae 

13 


194 


NON-METALLIC   ELEMENTS. 


is  changed  into  sulphuric  acid,  and  transforms  the  nitric  acid 
into  hyponitrac  acid,  thus  renewing  the  reaction  continually. 
Thus,  S03+N05-}-?iHO  =  S03+7*HO-f  N04.  In  this  way 
a  small  quantity  of  nitric  acid  can  be  made  to  oxydize  an 
indefinite  amount  of  sulphurous  acid ;  serving  the  purpose, 
as  it  were,  of  a  carrier  of  oxygen  from  the  atmospheric  air 
to  the  sulphurous  acid.  Meanwhile  the  water  on  the  floor 
of  the  chamber  grows  rapidly  acid ;  and  when  it  has  attained 
a  specific  gravity  of  about  1-5,  it  is  drawn  off  and  concen- 
trated by  boiling,  first  in  open  pans  of  lead  until  it  becomes 
strong  enough  to  corrode  the  lead,  and  afterward  in  stills 
of  platinum  until  it  has  a  density  of  about  1-8,  in  which  stato 
it  is  sold  in  carboys,  or  large  bottles,  packed  in  boxes. 

318.  The  process  of  forming  sulphuric  acid  is  easily 
illustrated  in  the  class-room  by  an  arrangement  of  apparatus 
like  that  shown  in  fig.  242.  Two  flasks  o  e  are  so  connected 


Fig.  242. 

by  bent  tubes  with  a  large  balloon,  that  from  one  b  sulphurous 
acid,  and  from  the  other  e  deutoxyd  of  nitrogen  are  supplied 
to  the  large  balloon  r.  A  third  flask  w  furnishes  steam  as  it 
is  wanted.  Fresh  air  must  be  occasionally  blown  in  at  the 
open  tube  t,  the  effete  products  escaping  at  o.  Thus  arranged, 
the  reactions  above  described  take  place.  If  but  little  vapor 
of  water  is  present,  the  sides  of  the  globe  are  soon  covered 

What  is  the  density  of  SO,  in  the  chambers  ?     318.  Explain  the  figur* 
and  process  242. 


SULPHUR  195 

with  a  white  crystalline  solid,  which  appears  to  be  a  compound 
of  sulphurous  and  of  nitrous  acids  (SOa,N04.)  This  sub- 
stance is  decomposed  by  a  larger  quantity  of  water  into  sul- 
phuric acid  and  hyponitric  acid,  and  as  it  is  known  to  be 
formed  in  the  leaden  chambers  in  large  quantities,  it  is  sup- 
posed to  have  an  important  influence  in  the  production  of  sul- 
phuric acid. 

319.  This  process  by  the  leaden  chambers  is  known  in 
the  arts  as  the  English  process  for  sulphuric  acid.    Formerly 
sulphuric  acid  was  procured  by  distilling  dry  sulphate  of 
iron  (green  vitriol)  in  earthenware  retorts,  at  a  high  tem- 
perature.    The  oily  fluid  thus  obtained  was  hence  vulgarly 
called  oil  of  vitriol.    This  old  process  is  still  in  use  at  Nord- 
hausen,  in  the  Hartz  Mountains,  producing  an  acid  which  is 
commonly  known  as  Nordhausen  acid.     It  is  the  most  con- 
centrated form  possible  for  fluid  sulphuric  acid.     Sulphuric 
acid  unites  with  water  in  four  proportions,  forming  definite 
compounds,  namely : 

Nordhausen  acid,  sp.  gr.  1-9  2(SO»)HO 

Oil  of  vitriol,  "  l'S3 SO,,HO 

Acid  of  "  1-78 S03,HO-f-HO 

Acid  of  "  1-63 S08,HO-j-2H 

320.  Nordhausen  acid  is  a  dark-brown,  oily  fluid,  fum- 
ing when  exposed  to  air,  and  hissing  like  a  hot  iron  when 
water  is  let  fall  into  it  drop  by  drop.     To  mingle  the  two 
rapidly  in  any  quantity  is  unsafe.     Cautiously  heated  in  a 
retort  protected  by  a  hood  of  earthenware  A,  as  in  fig.  243, 


319.  What  is  this  process  called  ?  What  was  the  old  one  ?  Whence 
the  vulgar  name  ?  What  is  the  most  concentrated  S03  ?  What  hydrates 
of  SO,  ?  What  of  Nordhausen  S03  ? 


196  NON-METALLIC   ELEMENTS. 

a  white,  crystalline,  silky  product  distils  over  and  is  col« 
lected  in  the  cool  receiver.  This  is  anhydrous  sulphuric 
acid  S03.  It  does  not  possess  acid  properties  by  itself,  but 
by  contact  with  water  or  moisture  it  is  changed  to  common 
sulphuric  acid.  It  must  be  preserved  in  tubes  hermetically 
sealed.  It  has  therefore  been  inferred  that  sulphuric  acid 
cannot  exist  without  water,  or  that  water  is  essential  to  the 
acid  property.  In  this  case  it  is  supposed  that  the  oxygen 
of  the  water  joins  that  already  with  the  sulphur,  (forming 
S04,)  while  the  new  compound  thus  produced  unites  with 
hydrogen,  forming  S04H. 

321.  When  exposed  to  a  temperature  of  —  29°,  sulphuric 
acid  freezes;  and  acid  of  1*78  exposed  to  a  temperature  of 
32°  freezes  in  large  crystals.    One  hundred  parts  of  concen- 
trated sulphuric  acid  contain  81-64  real  acid,  18-36  water, 
SO?HO.    At  620°  it  boils,  giving  off  a  dense,  white,  and  very 
suffocating  vapor.     It  is  intensely  acid  to  the  taste,  and 
deadly,  if  by  any  accident  it  is  swallowed,  corroding  and 
burning  the  organs  with  intense  heat.     It  blackens  nearly 
all  inorganic  matters,  charring  or  burning  them  like  fire.    Its 

strong  disposition  for  water  enables 
us  to  employ  it  in  desiccation,  and 
in  the  absorption  of  aqueous 
vapor;  using  for  this  purpose  a 
shallow  pan  (fig.  243)  containing 
Fig.  244.  S03HO,  while  the  substance  to  be 

dried  is  placed  above  it,  and  the  whole  then  covered  with  a 

low  bell-jar  or  a  tight-fitting  plate. 

322.  Great  heat  is  generated  from  the  mixture  of  4  parts 
by  weight  of  strong  sulphuric  acid  and  1  of  water,  and  a 
diminution  of  bulk  attends  the  mixing.     The  temperature 

rises  as  high  as  200°.  So  that  water  in  a  test  tube 
b  (fig.  245)  may  be  made  to  boil  when  placed  in 
the  mixture  contained  in  the  beaker-glass  a.  If 
common  sulphuric  acid  is  used  for  this  purpose,  it 
becomes  milky  when  water  is  added  to  it,  from  the 
precipitation  of  sulphate  of  lead,  derived  from  the 
ls'  4  '  boilers  in  which  it  was  made.  This  salt  is  soluble  in 

strong  sulphuric  acid,  but  is  precipitated  by  addition  of 

water. 

How  is  crystalline  SO,  obtained?  What  formula  is  given?  321. 
When  does  SO,  freeze  ?  What  of  sp.  gr.  1-78  ?  Give  other  traits  of  SO,. 
322.  What  if  water  and  S03  are  mingled  ?  Why  is  the  mixture  milky  ? 


SULPHUR. 


197 


323.  Sulphuric  acid  forms  sulphates,  a  class  of  salts  most 
minutely  known  to  chemists,  and  many  of  which  are  fami- 
liarly known  in  common  life. 

Chloride  of  barium,  added  to  sulphuric  acid,  or  to  a  soluble 
sulphate,  throws  down  an  abundant  precipitate  of  sulphate 
of  baryta,  a  salt  insoluble  in  all  menstrua.  The  same  test 
gives  a  precipitate  also  with  sulphurous  acid,  (sulphite  of 
baryta,)  but  the  latter  is  soluble  in  chlorohydric  acid. 

324.  There  are  several  chlorids  of  sulphur.    The  apparatus 
figured  in  fig.  245  shows  the  manner  of  preparing  one  of 


Pig.  246. 

them  ClSa.  Sulphur  is  placed  in  the  small  retort  P  and 
fused  by  the  lamp  beneath,  while  a  current  of  chlorine  libe- 
rated from  the  ballon  c,  and  dried  over  the  chloride  of  cal- 
cium tube  a,  is  delivered  gently  by  the  descending  tube  almost 
in  contact  with  the  fused  sulphur  in  P.  Combination  en- 
sues, chloride  of  sulphur  distils  over  and  is  condensed  in  the 
receiver  r,  kept  cool  by  water  from  the  fountain.  This 
chlorid  of  sulphur  is  a  reddish-yellow  fluid,  of  a  disagreeable 
odor.  It  boils  at  280°,  giving  a  vapor  of  density  4-668. 
The  density  of  the  liquid  is  1'68.  Water  decomposes  it, 
forming  sulphur  and  chlorohydric  acid.  One  volume  of  this 
substance  in  vapor  is  formed  of 

1  vol.  chlorine 2-440 

J    "    sulphur  G-f* 2-218 

Giving  the  theoretical  density 4-658 


While  experiment  gives 4-668 

323.  What  salts  does  SO,  form?  What  tests  for  SO,?  324.  ETow  is 
CIS,  formed?  Describe  fig.  245.  What  are  its  characters?  Give  iti 
volume  and  density. 


198  NON-METALLIC   ELEMENTS 

The  bromids  and  iodids  of  sulphur  possess  very  little 
interest. 

SELENIUM. 

Equivalent,  40.      Symbol,  Se.     Density,  4-3. 

325.  History   and  Properties. — This   element   was   dis- 
covered by  Berzelius,  in  1818,   and  named   by  him  from 
sdcne,  the  moon.     It  is  associated  in  nature  with  sulphur 
in  some   kinds  of  iron    pyrites,    and  in   a  lead    ore  from 
Saxony,  and  also  at  the  Lipari  Islands  combined  with  sul- 
phur and  accompanied  by  other  volcanic  products. 

It  closely  resembles  sulphur  in  most  of  its  properties,  as 
well  as  in  its  natural  associations.  At  common  tempera- 
tures it  is  a  brittle  solid,  opake,  and  having  a  metallic  lustre 
like  lead,  but  in  powder  it  is  of  a  deep  red  color.  Its 
specific  gravity  is  4'28  for  the  vitreous,  and  4-80  for  the 
granular  variety  from  slow  cooling.  It  softens  at  212°, 
and  may  then  be  drawn  out  into  red-colored  threads }  at  a 
little  higher  temperature  it  melts  completely,  and  boils  at 
650°,  giving  a  deep  yellow  vapor  without  odor.  It  passes 
through  the  same  changes  of  state  by  heat  as  sulphur.  It 
is  insoluble.  When  heated  in  the  air,  it  combines  with 
oxygen,  and  gives  out  a  disagreeable  and  strong  odor,  like 
putrid  horse-radish.  Before  the  blowpipe,  on  charcoal,  it 
burns  with  a  pale  blue  flame,  and  5^  of  a  grain,  so  heated, 
will  fill  a  large  apartment  with  its  odor.  It  is  a  non-con- 
ductor of  heat  and  of  electricity,  and  excites  resinous  elec- 
tricity. 

326.  The  compounds  of  selenium  with  oxygen  are  three, 
two  of  which  are  acids,  analogous  to  sulphurous  and  sul- 
phuric acids.     They  are — 

Oxyd  of  selenium SeO 

Selenious  acid SeO» 

Selenic  acid SeOf 

Oxyd  of  selenium  is  formed  when  selenium  is  heated  in 
the  air.  It  is  a  colorless  gas,  and  possesses  the  strong  odor 
before  mentioned. 

327.  Selenious  acid  is  formed  when  selenium  is  burned 


325.  What  of  selenium?     Give  its  characters.     Its  equivalent.     326 
What  compounds  of  0  has  it? 


SELENIUM. — TELLURIUM  — NITROGEN.  199 

in  a  current  of  oxygen  gas,  as  in  the  tube  a,  (fig.  247.)  A 
small  portion  of  selenium  is  placed  at  b, 
and  fused  by  a  lamp ;  at  this  temperature, 
oxygen  flowing,  from  a  reservoir,  in  at  a, 
combines  with  the  selenium,  forming  Se03, 
which  is  a  white  crystalline  body,  very  so- 
luble in  water,  and  sublimed  by  heat  un- 
changed. Selenic  acid  is  formed  when  sele- 
nium is  burned  by  nitrate  of  potash,  forming 
selenate  of  potash.  It  resembles  sulphuric 
acid  in  its  properties.  Both  selenious  and 
selenic  acids  form  salts  with  the  alkalies 
and  bases,  every  way  similar  to  the  sulphites  and  sulphates. 
Selenid  of  sulphur  is  found  native  among  volcanic  products. 


TELLURIUM. 

Equivalent,  64.     Symbol,  Te. 

328.  This  rare  substance  is  related  to  selenium  and  sul- 
phur.    It  forms  compounds  with  gold  and  bismuth,  found 
native  as  minerals.     Pure  tellurium  is  a  tin-white,  brittle 
substance,  with  a  metallic  lustre,  and  density  of  6-26.     It- 
melts  at  low  redness,  and  takes  fire  in  the  air,  forming  tel- 
lurous  acid,  Te03.     With  hydrogen  it  forms  a  compound, 
analogous   to    arseniuretted    hydrogen,   and    sulphuretted 
nydrogen. 

CLASS  IV. 

NITROGEN,   OR  AZOTE. 

Equivalent,  14.     Symbol,  N.     Density,  -972. 

329.  Preparation  and  History. — This   gas   forms   four- 
fifths  of  the  air,  and  is  an  essential  constituent  of  most 
organic  substances.    It  was  first  described  by  Rutherford,  in 
1772.    It  is  only  mingled  mechanically  with  oxygen  in  our 
atmosphere,  which  is  not  a  chemical  compound. 

It  is  most  easily  procured  for  purposes  of  experiment 
from  the  atmosphere,  by  withdrawing  the  oxygen  of  the  air 

327.  What  of  selenious  acid  ?    328.  What  of  tellurium  ?    329.  Give  ihe 
history  of  nitrogen. 


200 


NON-METALLIC   ELEMENTS. 


by  phosphorus.  This  is  easily 
done  by  burning  some  phos- 
phorus in  a  floating  capsule, 
under  an  air-jar,  upon  the  pneu- 
matic cistern,  (fig.  '248.)  The 
strong  affinity  of  phosphorus  foi 
oxygen  enables  it  to  withdraw 

^_  every    trace     of    this    element, 

i  leaving   behind  nitrogen  nearly 
__  pure,  containing  about  ^th  of 

— —  phosphorus.     The  water  soon  ab- 
sorbs the  snow-white  phosphoric 

acid.  The  first  combustion  of  the  phosphorus  expels  a 
portion  of  the  air  by  expansion  ;  but  as  the  combustion  pro- 
ceeds, the  water  rises  in  the  jar,  until  it  occupies  about 
Jth  of  its  space.  When  this  experiment  is  performed  over 
mercury,  the  white  phosphoric  acid  remains  unchanged. 
Nitrogen  may  be  procured  pure  by  passing  a  current  of  air 
over  copper  turnings  in  a  tube  of  hard  glass  heated  to 
redness :  the  oxygen  is  all  retained  by  the  copper,  while 
nitrogen  is  given  off.  Nitrogen  can  also  be  obtained,  by 
decomposing  strong  water  of  ammonia,  by  chlorine  gas : 
the  ammonia  yields  its  hydrogen  to  the  chlorine,  and  the 
nitrogen  is  given  off.  The  apparatus  (fig.  249)  may  be 

used  for  this 
purpose,  in 
which  p  is 
an  evolution- 
flask  for  chlo- 
rine, and  the 
strong  am- 
monia water 
is  in  10.  Great 
care  should 
be  taken  to 
prevent  all 
the  ammonia 
becoming  sa- 
turated, as  in 
Fig.  249.  that  case  a 


How  prepared  ?     How  from  ammonia  ?     What  precaution  is  notei  ? 
is  the  reaction  ? 


WITROGEN.  201 

very  dangerous  compound  (chloride  of  nitrogen)  will  be 
formed  by  the  action  of  the  chlorine,  on  the  chlorid  of  am- 
monia produced  in  the  process.  The  nitrogen  collects  in  n. 
3Cl-fNH3=3HCL-fN. 

330.  The  properties  of  nitrogen  are  mostly  negative.     It 
is  a  colorless,  tasteless,  odorless,  permanent  gas.    It  has  not 
been  liquefied.     It  combines  directly  with  no  element,  but 
indirectly  it  enters  into  most  powerful  combinations.    In  the 
atmosphere  it  appears  to  act  chiefly  as  a  diluent  of  oxygen. 
Its  density  is  0-972,  or  a  little  less  than  air.     A 

taper  immersed  in  it  (fig.  250)  is  extinguished  im- 
mediately. An  animal  placed  in  nitrogen  dies  from 
want  of  oxygen,  and  not  because  of  any  poisonous 
character  in  the  gas,  as  might  be  inferred  from  its 
abundance  in  our  atmosphere.     Hence  its  name 
azote,  from  a  privative,  and  the  Greek  zoe,  life,  to 
deprive  of  life.     Nitrogen  is  derived  from  Latin 
nitriuniy  nitre,  and  gennao,  I  form.    One  hundred       g'       ' 
volumes  of  water  dissolve  about  two  and  a  half  volumes  of 
nitrogen. 

The  Atmosphere. 

331.  The  mechanical  properties  of  the  atmosphere  have 
already  been  considered,  (20.)     The  number  and  propor- 
tion of  the  constituents  of  the  atmosphere   are  constant, 
although  their  union  is  only  mechanical.  Repeated  analyses 
have  shown  that  atmospheric  air  is  always  formed  of  nitro- 
gen, oxygen,  watery  vapor,  a  little  carbonic    acid,  traces 
of  carburetted  hydrogen,  and  a  small  quantity  of  ammo- 
nia.    The  air  on  Mount  Blanc,  or  that  taken  in  a  bal- 
loon by  Gay-Lussac  from  21,735  feet   above  the    earth, 
had  the  same  chemical  composition  as  that  on  the  surface, 
or  at  the  bottom  of  the  deepest  mines.     The  carbonic  acid, 
being  liable   to  changes  in  quantity  from  local  causes,  is 
found  to  vary  slightly. 

To  the  constituents  already  named,  we  may  add  the  aroma 
of  flowers  and  other  volatile  odors,  and  those  unknown, 
mysterious  agencies,  which  affect  health,  and  are  called  mias- 
mata. From  the  results  of  numerous  analyses,  we  state  the 
composition  of  the  atmosphere  in  100  parts,  to  be — 

330.  What  its  properties?  What  its  function  in  air?  How  affects 
life?  Hence,  what  name  has  it?  Define  the  word  nitrogen.  331. 
What  of  air?  How  are  its  constituents  ?  What  of  its  purity  ?  What 
aro  its  constituents  ? 


202 


NON-METALLIC   ELEMENTS. 


By  weight. 

Nitrogen 76-90  .. 

Oxygen 23-10  .. 


By  measure. 
....   79-10 
....  20-90 


100-00  100-00 

To  this  we  must  add  from  3  to  5  measures  of  carbonic 
acid  in  10,000  of  air,  about  the  same  quantity  of  carburetted 
hydrogen,  a  variable  quantity  of  aqueous  vapor,  and  a  trace 
of  ammonia.  Nitric  acid  is  also  sometimes  found  in  small 
quantity  in  rain-water,  formed  in  the  air  by  the  electrical 
discharges  of  thunder-clouds,  and  washed  out  by  the  rains. 
100  cubic  inches  of  dry  air  weigh  31-011  grains.  In  10,000 
volumes  the  constitution  of  the  air  will  be,  therefore — 

Nitrogen 7901 

Oxygen 2091 

Carbonic  acid 4 

Carburetted  hydrogen 4 

Ammonia trace 

10,000 

332.  The  analysis  of  air  is  accomplished  by  any  sub- 
stance which  will  remove  the  oxygen.  But  the  accurate 
performance  of  this  process  requires  numerous  minute  pre- 
cautions, any  notice  of  which  is  out  of  place  here.  Eu- 
diometry  is  the  term  applied  to  the  common  method  of 
analysis  for  air.  This  term  is  derived  from  Greek  words 
signifying  a  good  condition  of  the  air,  and  was  employed 
because  it  was  formerly  thought  that  an  analysis  of  the  air 
would  show  if  it  was  in  a  salutary 
condition.  One  of  the  simplest 
means  of  analyzing  the  atmosphere, 
consists  in  removing  the  oxygen 
by  the  slow  combustion  of  phos- 
phorus. For  this  purpose  a  stick  of 
phosphorus  is  sustained  on  a  plati- 
num wire  (fig.  251)inaconfinedpor- 
tion  of  air,  contained  in  a  graduated 
glass  tube,  whose  open  end  is  be- 
neath water.  A  gradual  absorption 
takes  place,  and  in  about  twenty- 
four  hours  the  water  ceases  to  rise 
in  the  tube,  by  which  we  know  that 
the  phosphorus  has  removed  all 


Fig.  251. 


Give  analyses  of  air?    What  is  its  composition  in  10,000  volumes" 
2.  How  analyzed?    What  is  eucliometry  ? 


NITROGEN.  203 

the  oxygen.  The  water  absorbs  the  resulting  phosphorous 
acid,  and  we  may  read  off,  by  the  graduation  on  the  tube, 
the  amount  of  oxygen  removed.  A  narrow-necked  bolt-head 
shows  this  result  in  a  more  striking  manner  in  the  class-room, 
the  large  volume  of  air  in  the  ball  causing  a  very  apprecia- 
ble rise  of  water  in  the  stem  during  the  course  of  a  lecture, 
(fig.  252.)  When  speaking  of  hydrogen,  we  will  mention 
another  method  of  eudiometry.  The  agency  of  the  air  in 
combustion  and  respiration  will  also  be  explained  under 
the  appropriate  heads.  The  air  dissolved  in  water,  and 
on  which  water-breathing  animals  live,  is  found  to  be 
decidedly  more  rich  in  oxygen  than  the  atmospheric  air. 
This  is  owing  to  the  fact  that  oxygen  is  much  more  abun- 
dantly absorbed  by  water  than  nitrogen,  in  the  proportion 
of  -0-iG  to  -025.  These  numbers  express,  respectively,  the 
ratio  of  solubility  of  the  two  gases  in  water.  The  air  in 
water  has  the  constitution — 

By  analysis.  By  theory. 

Oxygen 32  31-5 

Nitrogen 68  68-5 

100  100-0 

Compounds  of  Oxygen  and  Nitrogen. 

333.  Nitrogen  unites  with  oxygen,  forming  five  com- 
pounds, three  of  which  are  acids.  Their  names  and  consti- 
tution are  thus  expressed  : — 

Symbol. 

Protoxyd  of  nitrogen  (nitrous  oxyd) NO 

Deutoxyd  of  nitrogen  (nitric  oxyd) N0a 

Nitrous  acid NO, 

Hyponi trie  acid N04 

Nitric  acid N0§ 

As  nitric  acid  is  the  source  whence  all  the  other  com- 
pounds of  nitrogen  are  obtained,  we  will  commence  with 
the  history  of  that  compound  : — 

This  important  compound  was  known  in  the  earliest  days 
of  alchemy,  but  it  was  Cavendish  who,  in  1785,  first  made 
known  its  constitution.  He  formed  it  by  direct  union  of  its 
elements  over  a  solution  of  potash,  by  aid  of  a  series  of 
electrical  sparks  continually  passed  through  a  mixture 
of  the  two  gases  N  and  0,  for  several  successive  days, 

What  of  air  dissolved  in  water  ?  333.  What  are  the  oxygen  com- 
pounds  of  nitrogen?  Give  the  series.  What  is  the  source  of  other  ni- 
trogen compounds  ? 


204 


NON-METALLIC   ELEMENTS. 


in  a  close  tube,  (fig  253  ) 
The  ends  of  the  tube,  con- 
taining the  gases  and  pot 
ash  solution,  dipped  into 
and  contained  mercury  as 
a  conducting  medium  for 
the  electricity.  Nitre  was, 
Fig.  253.  subsequently,  found  in  the 

eolution,  thus  giving  the  strongest  evidence  of  a  union  of 
the  two  gases. 

334.  Nitric  Acid,  "Aqua  Fortis,"  N05HO.— This  power- 
ful acid  is  obtained  by  heating  saltpetre  (nitrate  of  potassa) 
or  nitrate  of  soda  with  strong  sulphuric  acid.  The  nitric 
acid  is  displaced  by  the  sulphuric,  and  distils  over,  being 
much  more  volatile  than  the  sulphuric  acid. 

335.  The  arrangement 
of  apparatus  required  is 
seen  in  figure  254.  The 
retort  R  contains  the 
nitre  in  small  crystals, 
and  should  be  supported 
in  a  sand-bath ;  or,  if  the 
quantity  of  nitre  does  not 
exceed  a  pound  or  two,  a 
naked  fire  answers  very 
well.  An  equal  weight 
of  sulphuric  acid  is  then 
added,  with  care  not  to 
soil  the  interior  neck  of 
the  retort.  Heat  is  gradu  • 
ally  applied,  and  the  re- 
Fig.  254.  ceiver  kept  cold  by  a  con- 
stant stream  of  water  distributed  over  its  surface  by  a 
piece  of  filtering  paper.  No  corks  or  luting  of  any  kind 
can  be  used  about  the  apparatus,  as  the  vapors  of  concen- 
trated nitric  acid  attack  all  organic  substances  with  energy, 
as  also  the  alumina  and  other  bases  of  clay-lute.  In  the 
first  moments  of  the  operation  the  vessels  are  filled  with 
deep-red  vapors  of  hyponitrous  acid,  due  to  the  decomposi- 
tion of  the  first  formed  portions  of  nitric  acid  by  the  great 


334.  What  is  the  history  of  NO,?    What  was  the  experiment  of  Ca- 
vendish ?     What  is  the  process,  fig.  254  ?     What  precautions  are  given  ? 


NITROGEN.  205 

excess  of  sulphuric  acid.  As  the  distillation  proceeds, 
the  vessels  become  colorless  and  the  distillate  very  nearly 
so.  The  red  vapors  appear  again  at  the  close  of  the  opera- 
tion, and  furnish  a  signal  when  to  arrest  the  process  and 
change  the  recipient.  This  is  because  the  temperature  rises 
toward  the  close,  to  the  decomposing  point  of  nitric  acid. 
The  bisulphate  of  potash  in  the  retort  remains  some  time 
after  the  heat  is  withdrawn  in  a  state  of  quiet  fusion,  having 
a  temperature  of  about  600°.  When  reduced  to  about  250°, 
hot  water  may  be  added  in  small  portions  at  a  time,  and 
with  care  the  retort  may  be  saved,  although  it  is  often 
sacrificed  from  the  crystallization  of  the  sulphate  of  potassa. 
In  the  arts  this  process  is  conducted  in  large  vessels  of  iron 
set  in  brick  furnaces. 

336.  Properties. — Nitric  acid  is  a  mobile  fluid,  nearly 
colorless,  fuming,  intensely  acid,  staining  the  skin  instantly 
yellow,  and  acting  with  great  energy  on  most  metals  and 
organic  substances.  It  has  usually  a  reddish  color,  due  to 
the  presence  of  hyponitric  acid.  When  most  concentrated 
it  has  a  density  of  1-51— 1'52,  and  contains  86  parts  in 
100,  real  acid.  It  boils  at  187°.  It  is  decomposed  by 
light,  evolving  red  fumes  of  hyponitric  acid  and  free  oxygen, 
which  sometimes  forcibly  expels  the  stopper.  It  should, 
therefore,  be  kept  in  a  dark  place,  or  in  black  bottles. 
Poured  on  pulverized  charcoal  which  has  recently  been 
ignited,  it  deflagrates  it  with  energy ;  warm  oil  of  turpentine 
is  immediately  fired  by  it;  and  its  action  on  phosphorus  is 
too  violent  to  be  a  safe  experiment,  without  great  precau- 
tion. The  concentrated  acid  freezes  at  — 40°;  but  if 
diluted  with  half  its  weight  of  water,  it  freezes  at  about  1$°. 
The  green  hydrous  acid  (343)  freezes  to  a  bluish-white  solid. 
The  dilute  acid  yields  by  distillation  a  product,  at  first  more 
concentrated,  but  when  it  has  a  boiling  point  of  250° 
the  product  is  of  uniform  strength,  and  contains  40  parts 
real  acid  in  100.  Like  sulphuric  acid,  it  forms  several 
definite  hydrates,  of  which  the  highest  is  the  strong  acid 
described  above.  Anhydrous  nitric  acid  N05  has  been  lately 
obtained  by  decomposing  dry  nitrate  of  silver  by  perfectly 
dry  chlorine.  Anhydrous  ntric  acid  crystallizes  in  colorless 
rhombs,  which  fuse  at  30°;  and  it  boils  at  50°  with  decoin- 

336.  What  are  the  properties  of  NO,?  How  does  it  act  on  combusti- 
bles ?  What  of  its  hydrates  ?  Of  anhydrous  NO,  ? 


206  NON-METALLIC   ELEMENTS. 

• 

position.  It  is  soluble  in  water,  evolving  much  heat,  and 
yielding  colorless,  hydrous  nitric  acid 

337.  Nitric  acid  is  a  powerful  solvent  of  the  metals,  and 
carries   them   to  their  highest  state   of  oxydation.      This 
action  is  always  attended  with  the  production  of  binoxyd  of 
nitrogen  N03  and  hyponitric  acid.     The  nitrates  are  all 
soluble  in  water.     When  fused  with  carbon  they  are  de- 
composed with  brilliant  deflagration  of  the  charcoal.    Nitrio 
acid  decolorizes  a  solution  of  sulphate  of  indigo,  and  with  a 
few  drops  of  chlorohydric  acid  it  dissolves  gold-leaf. 

Passed  in  vapor  through  a  porcelain  tube  heated  white- 
hot  it  is  decomposed,  yielding  nitrogen  and  oxygen. 

338.  Protoxyd  of  Nitrogen  NO,  Nitrous  Oxyd,  or  Laugh- 
ing Gas. — This  gaseous  compound  of  nitrogen  is  prepared 
by  heating  nitrate  of  ammonia  NH4O.N05  in  a  glass  flask; 

(fig.  255,)  by  the  aid  of  a  spiritrlamp. 
The  gas  is  given  off  at  about  400°  to 
500°,  and  is  delivered  by  the  bent  tube 
to  an  air-jar  on  the  pneumatic  trough. 
The  iiitrate  of  ammonia,  which  is  a 
crystalline  white  salt  formed  by  neu- 
tralizing dilute  nitric  acid  by  carbonate 
of  ammonia,  is  so  constituted  as  to  be 
resolved  by  heat  alone  into  nitrous 
oxyd  and  water;  thus,  NH4O.N05 
become  by  heat  4HO  -f  2NO  Con- 
sequently, the  equivalents  of  these  ele- 
ments show  us,  that  80  grains  of  nitrate 
of  ammonia,  will  yield  44  grains  of 
Fig.  255.  nitrous  oxyd,  and  36  grains  of  water. 

Care  must  be  taken  not  to  heat  this  salt  too  highly,  as  it  then 
yields  nitric  oxyd  and  hyponitric  acid.  If  a  red  cloud  is  seen 
during  any  part  of  the  operation,  the  heat  must  be  abated. 

339.  Properties. — Protoxyd  of  nitrogen  is  a  colorless  gas, 
with  a  faint,  agreeable  odor,  and  a  sweetish  taste.     With  a 
pressure  of  fifty  atmospheres  at  45°  F.  it  becomes  a  clear 
liquid,  and  at  about  150°  degrees  below  zero  freezes  into  a 
beautiful  clear  crystalline  solid.     By  the  evaporation  of  this 
solid,  a  degree  of  cold  may  be  produced  far  below  that  of 
the  carbonic  acid  bath  (151)  in  vacuo,  (or  lower  than  — 174° 

337.  How  does  it  affect  metals  ?  What  of  nitrates  ?  338.  How  is  NO 
prepared  ?  Give  the  reaction  ?  What  precaution  is  noted  ?  339.  What 
,ire  its  properties  ?  What  of  its  liquid  ?  What  temperature  ? 


NITROGEN.  207 

F.)  It  evaporates  slowly,  and  does  not  freeze,  like  carbonic 
acid,  by  its  own  evaporation.  The  specific  gravity  of 
nitrous  oxyd  is  1-527;  100  cubic  inches  of  it  weigh  47-20 
grains.  Cold  water  absorbs  about  its  own  volume  of  this 
gas.  It  cannot,  therefore,  be  long  kept  over  water,  but  may 
be  collected  over  the  water-trough  in  vessels  filled  with  warm 
water.  It  supports  the  combustion  of  a  candle, 
(fig.  256,)  and  sometimes  relights  its  red  wick  with 
almost  the  same  promptness  as  pure  oxygen. 
Phosphorus  burns  in  it  with  great  splendor. 
With  an  equal  bulk  of  hydrogen,  it  forms  a  mix- 
ture that  explodes  with  violence  by  the  electric 
spark  or  a  match  :  the  residue  is  pure  nitrogen, 
the  oxygen  forming  water  with  the  hydrogen. 
Passed  through  a  red-hot  porcelain  tube  it  is  re-  Flg>  256> 
solved  into  its  constituent  gases.  One  volume  of  protoxyd 
of  nitrogen  contains 

1  volume  of  nitrogen 0-972 

^  volume  of  oxygen 0-552 

Theoretical  density 1-524 

340.  It  may  be  breathed  without  injury,  but  it  produces 
a  remarkable  excitement  in  the  system,  amounting  to  in- 
toxication, and,  if  carried  far,  even  to  insensibility.  To  pro- 
duce these  effects  without  injury,  it  should  be  quite  pure, 
and  especially  free  fi«om  chlorine,  and  inhaled  through  a 
wide  tube,  from  a  gas-holder  or  bag.  The  presence  of  chlorid 
of  ammonium  in  the  nitrate  employed  should  be  especially 
avoided,  as  producing  chlorine.  There  is  a  sweetish  taste,  and 
a  sensation  of  giddiness,  followed  by  joyous  or  boisterous 
exhilaration.  This  is  shown  by  a  disposition  to  laughter,  a 
flow  of  vivid  ideas  and  poetic  imagery,  and  often  by  a  strong 
disposition  to  muscular  exertion.  These  sensations  are 
usually  quite  transient,  and  pass  away  without  any  resulting 
languor  or  depression.  In  a  few  cases,  dangerous  conse- 
quences have  followed  its  use,  and  it  should  always  be  em- 
ployed with  great  caution.  In  at  least  one  case,  in  the  labo- 
ratory of  Yale  College,  it  produced  a  joyous  exhilaration  of 
spirits,  which  continued  for  months,  and  permanent  restora- 
tion of  health.  Its  effects,  however,  on  different  individuals, 
are  various. 

How  does  it  act  on  combustibles  ?  What  is  its  volume  ?  340.  What 
its  effect  if  breathed  ? 


208  NON-METALLIC   ELEMENTS. 

341  Deutoxi/d  or  E'moxyd  of  Nitrogen,  Nitric  Oxyd.— 
This  gas  is  easily  prepared  by  adding  strong  nitric  acid  to 
clippings  of  sheet-copper,  contained  in 
a  bottle  arranged  with  two  tubes,  (fig. 
257.)  A  little  water  is  first  put  with  the 
copper  cuttings,  and  the  nitric  acid 
poured  in  at  the  tall  funnel-tube  until 
brisk  effervescence  comes  on.  In  this 
case  the  copper  is  oxydized  by  a  part  of 
the  oxygen  of  the  acid,  and  the  oxyd  thus 
formed  is  dissolved  by  another  portion  of 
acid.  The  nitrogen,  in  union  with  the 
two  equivalents  of  oxygen,  is  given  off 
as  nitric  oxyd,  which,  not  being  ab- 
sorbed by  water,  may  be  collected  over 
Fig.  257.  the  pneumatic-trough.  Many  other 

metals  have  the  same  action  with  nitric  acid.  The  action 
is  renewed  by  continued  additions  of  nitric  acid.  It  is 
also  obtained  very  pure  by  heating  nitrate  of  potash 
KO.N05  with  a  solution  of  protochlorid  of  iron  Fed,  in 
an  excess  of  chlorohydric  acid. 

342.  Properties. — Nitric  oxyd  is  a  transparent,  colorless 
gas,  tasteless  and  inodorous,  but  excites  a  violent  spasm  in 
the  throat  when  an  attempt  is  made  to  breathe  it.     It  has 
never  been  condensed  into  a  liquid.     Its  specific  gravity  is 
1-039,  and  100  cubic  inches  weigh  32-22  grains.     It  con- 
tains equal  measures  of  oxygen  and  nitrogen  uncondensed. 

A  lighted  taper  is  usually  extinguished  when  immersed 
in  it,  but  phosphorus  previously  well  inflamed  will  burn  in 
it  with  great  splendor.  When  this  gas  comes  into  contact 
with  the  air,  deep-red  fumes  are  produced,  by  its  union  with 
the  oxygen  of  the  air  to  form  hyponitric  ncid.  If  to  a  tall 
jar,  nearly  filled  with  nitric  oxyd,  standing  over  the  well 
of  the  cistern,  pure  oxygen  gas  be  turned  up,  deep  blood- 
red  fumes  instantly  fill  the  vessel,  much  heat  is  generated, 
and  a  rapid  absorption  results  from  the  solution  of  the  red 
nitrous  acid  vapors  in  the  water  of  the  cistern. 

343.  Nitric  oxyd  is  rapidly  absorbed  by  solution  of  green 
sulphate  of  iron,  forming  a  deep-brown  solution  of  sulphate 
of  peroxyd  of  iron.     Colorless  nitric  acid  also  absorbs  nitric 

341.  What  of  NO,?  How  evolved  ?  342.  Give  its  properties.  Why 
irrespirable  ?  How  affects  combustibles  ?  In  contact  with  air  produces 
what  ?  Give  an  illustration.  343.  What  absorbs  it  ? 


NITROGEN. 


209 


oxyd,  and  acquires  first  a  yellow,  then  an  orange-red,  and 
finally  a  lively  green  color.  This  operation  is  best  con- 
ducted in  an  apparatus  of  bottles  arranged  as  in  fig.  258, 
and  called  Woulf's  apparatus.  The  gas  generated  in  a  passes 


Fig.  258. 

in  succession  into  the  fluid  of  each  vessel.  The  central  tubes 
serve  as  safety-tubes.  The  colors  named  above  are  beauti- 
fully seen  in  the  several  bottles,  the  first  becoming  green 
before  the  last  has  gained  an  orange  tint.  By  carefully 
heating  the  green  acid,  the  hyponitric  acid  contained  in  it 
may  be  expelled.  The  deutoxyd  of  nitrogen  decomposes 
the  nitric  acid,  forming  hyponitric  acid,  (345.) 

344.  Nitrous  Acid,  N03. — This  is  a  thin,  mobile  liquid, 
formed  from  the  mixture  of  four  measures  of  deutoxyd  of 
nitrogen  with  one  measure  of  oxygen,  both  perfectly  dry, 
and  exposed  after  mixture  to  a  temperature  below  zero  of 
Fahrenheit.     It   has  an  orange-red  vapor  :    the  liquid  at 
common  temperatures  is  green,  but  at  zero  is  colorless. 
Water  decomposes  it,  forming  nitric  acid  and  deutoxyd  of 
nitrogen.     It  forms  salts,  called  nitrites. 

345.  Hyponitric  Acid,   N04. — When  the  green  nitric 
acid  obtained  in  the  process  just  described   (fig.  258)  is 
cautiously  distilled,  hyponitric  acid  in  notable  quantity  is 
collected  in  the  refrigerated  receiver.     The  apparatus  is  ar- 
ranged as  in  fig.  259.     The  green  acid  is  heated  in  the  retort 
r,  by  means  of  a  water-bath  w,  over  the  lamp  <?,  and  the  pro- 
duct is  collected  in  the  U  tube  t,  placed  in  a  refrigerant  mix- 
ture.    This  acid  is  also  procured  by  decomposing  nitrate  of 
lead  in  a  porcelain  retort  by  heat.     Oxygen  and  hyponitric 

How  does  it  affect  NO,?     Explain  the  apparatus,  fig.  257.     344.  What 
of  NO  ?     What  are  its  salts?     345.  How  is  N04  obtained? 

U 


210  NON-METALLIC   ELEMENTS. 

acid  are  obtained,  and  the  latter  is  collected  as  above.     This 
is  an  orange-colored  fluid,  density  1-42,  becoming  red  when 


Fig.  259. 

heated.  It  boils  at  82°,  and  solidifies  at  8°.  Its  vapor  ia 
intensely  red,  and  has  the  density  1-73.  This  compound  is 
hardly  entitled  to  be  considered  as  an  acid,  it  does  not  form 
salts,  but  in  contact  with  a  base  is  decomposed,  producing 
a  nitrate  and  a  nitrite. 

PHOSPHORUS. 

Equivalent,  32.  Symbol,  P.  Density,  1-863. 
.  346.  History. — Phosphorus  is  an  element  nowhere  seen 
free  in  nature,  but  it  exists  largely  in  the  animal  kingdom, 
combined  with  lime,  forming  bones,  and  is  found  also  in 
other  parts  of  the  body.  In  the  mineral  kingdom  it  exists 
widely  diffused  in  several  well-known  forms,  particularly  in 
the  mineral  called  apatite,  which  is  a  phosphate  of  lime. 
It  is  introduced  into  the  animal  system  by  the  plants  used 
as  food,  whose  ashes  contain  a  notable  quantity  of  phos- 
phate of  lime.  It  was  discovered  in  1669,  by  Brandt,  an 
alchemist  of  Hamburg,  while  engaged  in  seeking  for  the 
philosopher's  stone,  in  human  urine.  Its  name  implies  its 
most  remarkable  property,  (phos,  light,  and  pliero,  I  carry.) 
847.  Preparation. — Phosphorus  is  procured  in  immense 

How  as  in  fig.  258  ?     What  are  its  properties  ?    346.  Givo  the  history 
of  phosphorus.    Whence  its  name  ? 


PHOSPHORUS. 


211 


quantities  from  burnt  bones,  for  the  manufacture  of  friction 
matches.  The  bones  are  calcined  until  they  are  quite 
white ;  they  are  then  ground  to  a  fine  powder,  and  fifteen 
parts  of  this  are  treated  with  thirty  parts  of  water  and  ten 
of  sulphuric  acid  :  this  mixture  is  allowed  to  stand  a  day  or 
two,  and  is  then  filtered,  to  free  it  from  the  insoluble  sul- 
phate of  lime,  formed  by  the  action  of  the  oil  of  vitriol  on 
the  bones.  The  clear  liquid  (which  is  a  soluble  salt  of  lime 
and  phosphoric  acid)  is  then  evaporated  to  a  syrup,  and  a 
quantity  of  powdered  charcoal  added.  The  whole  is  then 
completely  dried  in  an  iron  vessel  and  gently  ignited.  After 
this,  it  is  introduced  into  a  stoneware  or  iron  retort,  to 
which  a  wide  tube  of  copper  is  fitted,  communicating  with  a 
bottle  in  which  is  a  little  water,  that  just  covers  the  open 
end  of  the  tube,  (fig.  260 :)  a  small 
tube  carries  the  gases  given  out  to  a 
chimney  or  vent.  The  retort  being 
very  gradually  heated,  the  charcoal 
decomposes  the  phosphoric  acid,  car- 
bonic acid  and  carbonic  oxyd  gases  are 
evolved,  and  free  phosphorus  flows 
down  the  tube  into  the  bottle,  where  it 
is  condensed.  The  operation  is  a  criti- 
cal one.  Splendid  flashes  of  light  are 
constantly  given  out  during  the  ope- 
ration, from  the  escape  of  phosphu- 
retted  hydrogen.  The  crude  phos- 
phorus thus  obtained  is  purified  by 
melting  under  water,  and  it  is  then  cast  into  glass  tubes, 
forming  the  sticks  in  which  it  is  sold. 

348.  Properties. — Phosphorus  is  an  almost  colorless,  semi- 
transparent  solid,  which  at  ordinary  temperatures,  cuts  with 
the  consistency  and  lustre  of  wax.  At  32°  it  is  brittle, 
and  breaks  with  a  crystalline  fracture.  Exposed  to  light,  it 
soon  becomes  yellow  and  finally  red.  Its  density  by  the 
late  determinations,  is  1-826-1-840,  and  liquid  1-88.  It  is 
insoluble  in  water;  but  dissolves  readily  in  bisulphuret  of 
carbon ;  in  ether,  alcohol,  and  various  oils,  it  is  partially 
soluble.  It  is  obtained  in  fine  dodecahedral  crystals,  from 
its  solution  in  bisulphuret  of  carbon.  It  melts  at  111°  to 


Fig.  260. 


347.  How   prepared?     How   is   the   crude   PO.    decomposed?    348. 
What  are  its  characters  ?     How  crystallized  ?    How  soluble  ? 


212  NON-METALLIC  ELEMENTS. 

a  limpid  liquid  :  when  fused  beneath  water,  it  is  safely  re- 
cast  in  small  sticks,  by  drawing  it  into  narrow  glass  tubes. 
It  boils  at  554°,  forming  a  colorless  vapor  with  the  density 
4-226.  Owing  to  its  great  inflammability,  it  is  a  very  un- 
safe substance  to  handle,  producing  severe  burns,  very  dif- 
ficult to  heal.  Any  impurity,  such  as  the  presence  of  partly 
oxydized  phosphorus,  as  from  the  nitrogen  experiment, 
(fig.  248)  renders  it  much  more  liable  to  inflammation.  The 
heat  of  the  hand,  or  the  least  friction,  suffices  to  set  fire  to 
it.  It  must  be  kept  under  water,  to  which  alcohol  enough 
may  be  added  to  prevent  its  freezing  in  winter.  If  exposed 
to  the  air,  it  wastes  slowly  away,  forming  phosphorous  acid. 
When  in  the  dark,  it  is  seen  to  be  luminous.  The  vapor 
which  comes  from  it  has  a  strong  garlic  odor,  which  does 
not  belong,  either  to  the  pure  phosphorus,  or  its  acid  com- 
pounds. By  this  action  the  ozone  of  Schonbein  is  formed, 
(279.)  A  little  olefiant  gas,  the  vapor  of  ether,  or  any 
essential  oil,  will  entirely  arrest  the  slow  oxydation  of  phos- 
phorus in  air.  The  presence  of  nitrogen  or  hydrogen  seems 
to  be  essential  to  this  operation,  as,  in  pure  oxygen,  phos- 
phorus does  not  form  phosphorous  acid  at  common  temper- 
atures. It  burns  in  pure  oxygen  gas  with  great  splendor, 
forming  one  of  the  most  brilliant  experiments  in  chemistry, 
(354.)  Phosphorus  is  a  violent  poison. 

349.  Red,  or  amorphous  phosphorus,  is  a  peculiar  iso- 
meric  modification  of  common  phosphorus,  produced  by  heat- 
ing it  for  a  long  time  near  its  point  of  vaporization,  in  an 
atmosphere  of  hydrogen,  or  of  carbonic  acid.  This  effect 
takes  place  also  when  phosphorus  is  long  exposed  to  the 
light :  the  exterior  of  the  sticks  becomes  encrusted  with  a 
red  powder,  formerly  supposed  to  be  oxyd  of  phosphorus. 
Red  phosphorus  presents  properties  strikingly  different  from 
common  phosphorus:  the  latter  fuses,  as  we  have  seen,  at  111°; 
the  former  remains  solid  even  at  482°,  and  at  500°  returns 
to  the  condition  of  ordinary  phosphorus.  Red  phosphorus 
can  be  preserved  without  change  in  air,  has  no  sensible 
odor,  and  may  even  be  heated  to  392°  without  becoming 
luminous.  Its  specific  gravity  is  1-964.  It  does  not  com- 
bine with  sulphur  at  the  fusion  point  of  that  body,  while 

What  renders  it  more  inflammable  ?  How  is  it  kept  ?  If  exposed  to 
air,  what  happens  ?  How  is  its  combustion  in  0  managed  in  fig.  264  ? 
349.  What  is  red  phosphorus  ?  How  produced  ?  Give  its  characters. 
How  is  it  recognized  as  the  same  bod/  ? 


PHOSPHORUS.  213 

common  phosphorus  unites  with  sulphur  with  a  terrible  ex- 
plosion. It  is  only  from  the  identity  of  the  compounds 
from  these  two  modifications  of  phosphorus  that  it  is  shown 
that  they  are  indeed  one  and  the  same  body.  The  red 
phosphorus  is  preferred,  from  its  greater  safety,  in  the  manu- 
facture of  matches,  and  in  medicine. 

Compounds  of  Phosphorus  with  Oxygen. 

350.  The  compounds  of  phosphorus  with  oxygen  are 
four  in  number,  namely  : 

Oxyd  of  phosphorus PaO 

Hypophosphorous  acid PO 

Phosphorous  acid P0t 

Phosphoric  acid PO* 

351.  Oxyd  of  phosphorus  is  formed  when  a  stream  of 
oxygen  gas  is  allowed  to  flow   from  a  tube 

upon  phosphorus,  melted  under  warm  water, 
as  seen  in  fig.  261.  The  phosphorus  burns 
under  water  and  forms  a  brick-red  powder, 
which  is  the  oxyd  in  question,  mingled  with 
much  unburnt  phosphorus.  The  presence  of 
oxyd  of  phosphorus  with  unburnt  phosphorus 
renders  the  latter  much  more  inflammable. 
The  water  over  the  oxyd  of  phosphorus  in 
this  experiment  becomes  a  solution  of  phos- 
phorous and  phosphoric  acids. 

352.  Hypophosphorous  acid  is  a  powerful  deoxydizing 
agent,  decomposing  the  oxyds  of  mercury  and  copper,  and 
even  sulphuric  acid,  with  precipitation  of  sulphur  and  libe- 
ration of  sulphurous  acid :  by  these  reactions  it  becomes 
exalted  to  phosphorus  or  phosphoric  acid.     It  is  prepared 
by  decomposing  the  hypophosphite  of  baryta. 

353.  Phosphorous  acid  P03  is  formed  by  the  slow  com- 
bustion of  phosphorus  in  the  air  :  a  stick  of  phosphorus  ex- 
posed to  air  is  immediately  surrounded  by  a  white  cloud  of 
this  acid.     Sticks  of  phosphorus,  cast  in  small  glass  tubes, 
may  be  arranged  as  in  fig.  262,  in  a  funnel.     Each  stick  is 
placed  in  a  glass  tube  a  6,  slightly  larger  than  itself,  and  drawn 
to  a  point,  fig.  263 ;  and  these  are  arranged  in  a  funnel  and 

350.  What  are  the  0  compounds  of  P?    351.  How  is  PaO  formed? 
352.  What  of  PO  ?    353.  How  is  PO,  formed  ? 


NON-METALLIC   ELEMENTS. 

covered  with  an  open  bell, 
to  keep  out  dust  and.  the 
fluctuations  of  air.  The 
action  then  proceeds  gra- 
dually, and  a  considerable 
quantity  of  the  product 
is  collected  in  the  bottle 
beneath.  When  formed  by 
combustion  of  phosphorus 
in  a  limited  quantity  of 
air,  phosphorous  acid  is  a  Fiw>  2fi3 
dry  white  powder.  Con- 
tact of  humid  air  converts  it  into  the  above  form,  which 
always  contains  some  phosphoric  acid.  It  is  one  of  the  less 
powerful  acids.  By  heat  it  decomposes  the  oxyds  of  mer- 
cury and  silver.  It  forms  salts  called  phosphites. 

354.  Phosphoric  Acid,  P05. — This  acid  is  formed  by  the 
action  of  strong  nitric  acid  on  phosphorus,  as  well  as  from 
bones,  by  the  action  of  sulphuric  acid,  as  in  the  process  for 
obtaining  phosphorus,  (347.)  ^Iien  phosphorus  is  burned 
in  a  full  supply  of  oxygen  ,gtts^  this  acid  is  the  product. 
For  this  purpose,  an  arrangement  like  fig.  264  is  adopted. 


Fig.  262. 


Fig.  264. 

The  large  globe  is  filled  by  displacement  with  oxygen, 
dried  by  the  chlorid  of  calcium  vessel  c.  The  phosphorus 
is  burned  in  a  capsule,  supported  at  the  bottom  of  the  globe 
on  a  bed  of  dry  gypsum,  and  is  dropped  in  at  pleasure  by 
the  porcelain  tube  t,  whose  orifice  is  closed  by  a  cork.  The 

Describe  the  arrangement,  fig.  262.     What  are  its  properties  ?     354. 
How  is  P0»  formed  ? 


PHOSPHORUS.  215 

bottle  with  two  necks  receives  the  vapors  of  phosphoric  acid, 
a  draft  being  kept  up  by  the  porcelain  tube  p,  which  is 
made  to  act  as  a  chimney,  by  the  alcohol  flame  from  the 
cup  a.  In  this  way  the  combustion  is  kept  up  at  pleasure, 
as  fresh  oxygen  is  supplied  by  the  hose  p.  In  a  dark  room 
this  experiment  forms  a  most  magnificent  display  of  mellow 
light.  Such  is  its  avidity  for  water,  that  phosphoric  acid 
hisses  like  a  hot  iron  when  added  to  it.  It  makes  an  intensely 
acid  solution,  which,  evaporated  to  dryness  and  ignited,  yields 
on  cooling  a  transparent  glassy  solid,  called  glacial  phos- 
phoric acid. 

355.  Phosphoric  acid  forms  three  distinct  hydrates  with 
water,  and  three  classes  of  salts.     These  salts  give  a  beauti- 
ful example  of  the  substitution  of  a  metal  for  hydrogen  in 
the  production  of  salts.     Let  M  represent  a  metal  in  the 
following  formulae,  and  we  have 

Acids.  Salts. 

Monobasic  or  metaphosphoric  acid IIO.P05,  giving  metaphosphate    MO.POj 

Bibasic  or  pyrophosphoric  acid 2HO.PO&,     "      pyrophosphate  2MO.PO* 

Tribasic  or  common  phosphoric  acid 3IIO.PO»,     "      phosphate SMO.POs 

For  a  full  account  of  these  interesting  modifications  of 
phosphoric  acid,  the  student  is  referred  to  Dr.  Graham's 
excellent  Elements  of  Chemistry. 

The  compounds  of  phosphorus,  especially  the  phosphates 
of  lime  and  of  magnesia,  are  very  widely  distributed  in  nature, 
and  enjoy  an  important  function  in  the  economy  of  life. 
The  tribasic  phosphates  produce  with  nitrate  of  silver  a  yel- 
low precipitate  ;  with  solutions  of  magnesia  and  ammonia  a 
fine  granular  one,  (ammonio-phosphate  of  magnesia;)  and 
the  molybdate  of  ammonia  detects  the  smallest  trace  of  this 
acid  even  in  the  fluids  of  the  body. 

356.  Chlorids  of  Phosphorus. — Of  these  there  are  two, 
the  perchlorid    PC15,   and  the  terchlorid   PC13.      The  first 
is  formed  when  phosphorus  is  introduced  into  a  jar  of  dry 
chlorine.     It   inflames  and    lines    the   sides  of  the  vessel 
with  a  white  matter,  which  is  the  perchlorid  of  phosphorus. 
This  compound  is  very  unstable,  and  when  put  in  water  both 
it  and  the  water  suffer  decomposition,  and  hydrochloric  and 
phosphoric  acids  result.     To  form  the  other,  PC13,  the  appa- 
ratus used  for  the  chlorid  of  sulphur  may  be  employed,  sub- 
stituting phosphorus  for  sulphur  in  the  retort  P,  (fig.  245.) 

How  from  bones  ?  What  are  its  properties  ?  What  is  glacial  P08  ? 
355.  What  of  its  hydrates  ?  What  tests  for  POS  ?  356.  What  chloridi 
of  phosphorus  are  there  ?  How  is  PC13  formed  ? 


216  NON-METALLIC   ELEMENTS. 

The  bromids,  iodids,  and  sulphurets  of  phosphorus  have 
the  same  constitution  as  the  chlorids,  and  are  formed  by 
contact  of  the  elements.  They  are  unimportant,  and  the 
eulphuret  is  a  very  violent  and  dangerous  compound  to  form. 

CLASS  V.  THE  CARBON  GROUP. 

CARBON. 

Equivalent,  6.    Symbol,  C.    Specific  gravity  in  vapor,  0-829. 

357.  History. — Carbon  is  an  element  found  in  all  three 
kingdoms  of  nature.     Charcoal  and  mineral  coal,  which  are 
the  two  common  forms  of  carbon,  have  been  known  from 
the  remotest  times  of  history.     Its  great  importance  in  the 
daily  wants  of  society  makes  it  one  of  the  most  interesting 
of  the  elementary  bodies,  and  our  interest  in  it  is  not  dimin- 
ished from  the  fact  that  the  charcoal  and  mineral  coal  which 
we  use  as  fuel  and  the  black-lead  of  our  pencils  are,  essen- 
tially, the  same  thing  with  that  rare  and  costly  gem,  the 
diamond.     The  three  distinct  and  very  dissimilar  forms  of 
existence  which  this  element  assumes,  give  us  one  of  the 
best  examples  known  of  the  allotropism  of  bodies.     We  will 
very  briefly  mention  the  principal  characters  of  the  three 
forms  of  carbon:  1.  The  diamond;  2.  Graphite  or  plum- 
bago ;  3.  Mineral  coal  and  charcoal. 

358.  The  diamond  is  pure  carbon  crystallized.     It  takes 
the  forms  of  the  regular  system,  or  first  crystalline  class, 
(44,)  of  which  the  annexed  figures  are  some  of  the  common 
modifications.     Its  crystalline  faces  are  often  curved,  as  in 
fig.  266.     The  diamond  is  the  hardest  of  all  known  sub- 
stances, and  can  be  scratched  or  cut  only  by  its  own  dust. 


Fig.  266.        Fig.  267.        Fig.  268.  Fig.  269. 

The  solid  angles  of  this  mineral,  formed  by  the  union  of  curved 
planes,  are  much  used,  when  properly  set,  for  cutting  glass, 

What  of  the  bromids  and  sulphurets  ?  357.  Give  the  history  of  carbon. 
What  is  its  equivalent  ?  What  of  its  allotropism  ?  358.  What  of  the 
diamond  ? 


CARBON.  217 

which  it  does  with  great  ease  and  precision.  It  has  a  specific 
gravity  of  3'52,  and  the  highest  value  of  any  kind  of  treasure. 
The  most  esteemed  diamonds  are  colorless,  and  of  an  inde- 
scribable brilliancy,  described  as  the  "  adamantine  lustre. " 
They  are  often  slightly  colored,  of  a  yellowish,  rose,  blue, 
or  green,  and  even  black  tint.  The  largest  known  dia- 
mond formerly  belonged  to  the  Great  Mogul,  and  when 
found  weighed  2769-3  grains,  or  nearly  six  ounces:  it  had 
the  form  of  half  ahen's-egg.  The  Pitt,or  Regent  diamond, 
was  sold  to  the  Duke  of  Orleans  for  £130,000.  It  weighs 
less  than  an  ounce.  This  was  the  gem  which  Napoleon 
mounted  in  the  hilt  of  his  sword  of  state.  The  Koh-i-noor, 
or  mountain  of  light,  (the  Great  Mogul  diamond,)  which 
now  belongs  to  Queen  Victoria,  was  valued  to  the  British 
government  at  two  million  pounds  sterling,  but  its  com- 
mercial value  is  about  three  millions  of  dollars,  or  £622,000. 
It  weighed  before  its  recent  cutting,  1108  grains,  or  277 
carats.  This  gem  was  found  at  Golconda.  The  diamond  is 
usually  found  in  the  loose  sands  of  rivers,  and  is  gene- 
rally accompanied  by  gold  and  platinum.  Its  native  rock 
is  supposed  to  be  a  peculiar  flexible  kind  of  sandstone, 
called  itacolumite;  and  it  is  sometimes  found  loosely 
imbedded  in  a  ferruginous  conglomerate  in  Brazil.  A  few 
diamonds  have  been  found  in  the  United  States;  chiefly 
in  North  Carolina. 

359.  From  its  high  refractive  power  the  diamond  is  sup 
posed  to  be  of  vegetable  origin.     The  sun's  light  seems  to  be 
absorbed  by  the  diamond,  since  it  phosphoresces  beautifully 
for  some  time  in  a  dark  place,  after  it  has  been  exposed  to 
the  sun.     It  is  a  non-conductor  of  heat  and  electricity,  and 
is  very  unalterable  by  chemical   means.     It   is   infusible, 
and  not  attacked  by  acids  or  alkalies.   But  heated  to  redness 
in  the  air,  it  is  totally  consumed,  and  the  sole  product  of  its 
combustion  is  carbonic  acid  gas. 

360.  (2.)    Graphite  or  Plumbago. — This  form  of  carbon 
is  sometimes  improperly  called  "black-lead,"  but  it  does  not 
contain  a  trace  of  lead  in  its  composition,  and  bears  no  re- 
semblance to  it,  except  that  both  have  been  used  to  mark 
upon  paper. 

This  peculiar  mineral  is  found  in  the  most  ancient  rocks, 

Give  its  form  and  characters.  What  is  its  lustre  ?  What  are  some  of  the 
highly  valued  diamonds  ?  What  of  Koh-i-noor  ?  Where  is  the  diamond 
found?  359.  What  of  its  supposed  origin?  360.  What  is  plumbago? 


218  NON-METALLIC   ELEMENTS. 

as  well  as  with  those  of  a  more  modern  era.  It  is  also  fre- 
quently found  in  company  with  coal,  and  is  sometimes  formed 
artificially,  as  in  the  fusion  of  cast-iron.  It  almost  always 
contains  a  trace,  and  sometimes  several  per  cent,  of  iron, 
which  is,  however,  foreign  to  it;  otherwise  it  is  pure  carbon. 
It  is  very  much  used  for  making  pencils,  and  the  coarser 
sorts  are  manufactured  into  very  useful  and  refractory  melt- 
ing pots.  The  most  valued  plumbago  for  the  finest  drawing 
pencils  has  been  brought  chiefly  from  the  Borrowdale  mine, 
in  Cumberland,  England;  but  it  is  a  common  mineral  in 
this  country,  as,  for  instance,  at  Sturbridge  in  Massachusetts, 
St.  John  in  New  Brunswick,  and  many  other  places.  It  is 
found  crystallized  in  flat,  six-sided  prisms,  a  form  altogether 
incompatible  with  that  of  the  diamond.  It  is  soft,  flexible, 
and  easily  cut;  its  density  is  2-20;  feels  greasy,  and  marks 
paper.  It  is  quite  incombustible  by  all  ordinary  means,  but 
burns  in  oxygen  gas,  forming  only  carbonic  acid  gas,  and 
leaving  a  red  ash  of  oxyd  of  iron. 

361.  (3.)  Coal. — The  vast  beds  of  mineral  carbon,  known 
as  anthracite,  bituminous  coal,  brown  coal,  and  lignite,  are 
all  of  them  nearly  pure  carbon.     Of  the  first  two  of  these, 
no  country  has  such  abundant  and  excellent  supplies  as  the 
United  States.     These  accumulations  of  fuel  are  the  remains 
of  the  ancient  vegetation  of  the  planet,  which,  long  anterior 
to  the  creation  of  man,  a  bountiful  Providence  laid  away  in  the 
bowels  of  the  earth  for  his  future  use.    Bituminous  coal  differs 
from  anthracite  only  in  having  a  quantity  of  volatile  hydro- 
carbon united  with  it,  which  is  wanting  in  the   anthracite. 
This  opake  combustible  mineral  is  entirely  a  non-conductor  of 
electricity,  and  some  of  its  varieties  excite  resinous  electricity. 

362.  Charcoal  from  wood  is  the  carbonized  skeleton  of 
the  woody  fibre  which  is  found  in  all  plants.     The  best 
charcoal  is  made  by  heating  sticks  of  wood  in  tight  iron 
vessels,  without  contact  of  air,  until  all  gases  and  vapors 
cease  to  be  given  off.     A  great  quantity  of  acetic  acid,  tar, 
and  oily  matters,  with  water,  are  given  out,  and  a  jetty 
black,  brittle,  hard  charcoal  is  left  behind,  which  is  a  per- 
fect copy  of  the  form  of  the  original  wood.    It  is  a  non-con- 
ductor of  heat,  but  conducts  electricity  almost  as  well  as  a 
metal.     It  is  a  very  unchangeable  substance,  insoluble  in 

Where  found?  What  its  character?  361.  What  of  coal?  What  its 
origin  ?  What  difference  between  anthracite  and  bituminous  ?  What  of 
its  electrical  character?  362.  What  is  charcoal  ?  What  its  characters ? 


CARBON.  219 

water,  acids,  or  alkalies,  suffers  little  change  from  long  ex- 
posure to  air  and  moisture,  and  does  not  yield  to  the  most 
intense  heat  to  which  it  can  be  subjected,  if  air  is  excluded. 

363.  Charcoal  has  the  property  of  absorbing  gases  to  a 
most  remarkable  degree,  at  common  temperatures.     A  frag- 
ment of  recently  heated  charcoal,  of  a  convenient  size  to  be 
introduced  under  a  small  air-jar  over  the  mercurial  cistern, 
will  soon  take  up  many  times  its  own  volume  of  air,  as  will 
appear  by  the  rise  of  the  mercury  in  the  air-jar.     In  this 
case  it  absorbs  more  oxygen  than  nitrogen,  the  residual  air 
having  only  eight  per  cent,  of  oxygen  in  it.     On  heating, 
it  again  parts  with  the  gas  it  has  absorbed.     The  power  of 
absorption  seems  to  depend  entirely  on  the  natural  elasticity 
of  the  gas,  and  not  at  all  on  its  affinity  for  carbon.     Those 
gases  that  are  most  easily  reduced  to  a  fluid  condition  by 
cold  and  pressure,  are  most  abundantly  absorbed  by  char- 
coal.    Charcoal  from  hard  wood  with  fine  pores  has  this 
property  in  the  highest  degree.     Thus,  charcoal  from  box- 
wood freshly  prepared,  will  absorb  of  ammoniacal  gas  90 
times  its  own  volume ;  of  muriatic-acid  gas,  85  times  ;  of 
sulphuretted  hydrogen,  81  times  ;  of  nitrous  oxyd,  40  times; 
of  carbonic  acid,  32  times ;  of  oxygen,  9*25  times;  of  nitro- 
gen,  1-5    times;    and  of  hydrogen,   1-75  times   its   own 
volume. 

364.  Charcoal  also  has  the  power  of  absorbing  the  bad 
odors  and  coloring  principles  of  most  animal  and  vegetable 
substances.     Tainted  meat  is  made  sweet  by  burying  it  in 
powdered  charcoal,  and  foul  water   is  purified    by   being 
strained  through  it.     The  highly  colored  sugar-syrups  are 
completely  decolorized  by  being  passed  through  sacks  of 
animal  charcoal,  (bone-black,)  prepared  by  igniting  bones. 
It  also  precipitates  bitter  principles,  resins,  and  astringent 
substances  from  solution.     Common  ale  or  porter  becomes 
not  only  colorless,  but  also  in  a  good  degree  deprived  of  its 
bitter  principles,  by  being  heated  with  and  filtered  through 
animal  charcoal.     This  property  is  lost  by  use,  and  regained 
by  heating  it  afresh.    Its  power  of  absorption  seems  similar 
to  that  possessed  by  spongy  platinum,  (251.)     Hydrogen, 
in  small  quantity,  is  very  obstinately  retained  in  the  pores 
of  charcoal,  and  water  is  consequently  always  produced  from 


363.  What  of  its  absorbing  power?     What  regulates  its  power  with 
carious  gases  ?    364.  What  of  its  disinfecting  and  decolorizing  powers  ? 


220 


NON-METALLIC   ELEMENTS. 


the  combustion  of  carbon  in  pure  oxygen  gas.  Carbon  has 
a  greater  affinity  for  oxygen  at  high  temperatures  than  any 
other  known  substance,  and  for  this  reason  it  is  useful  in 
reducing  the  oxyds  of  iron  and  other  oxyds  to  the  metallic 
state.  Lamp-black  is  a  pulverulent  variety  of  carbon,  pro- 
duced from  the  imperfect  combustion  of  oils  and  resins. 

Compounds  of  Carbon  with  Oxygen. 

365.  The  compounds  of  carbon,  oxygen,  and  hydrogen 
embrace  a  majority  of  the  bodies  described  in  the  organic 
chemistry;  which  is  therefore  not  improperly  termed  the 
chemistry  of  the  carbon  series.     We  will  consider  at  pre- 
sent, however,  only  carbonic  acid  and  carbonic  oxyd. 

366.  Carbonic  Add,  C0a.—  History. — This  is  the    sole 
product  of  the  combustion  of  the  diamond  or  any  pure  carbon 
in  the  air,  or  in  oxygen  gas.     It  was  first  recognized  and 
described  by.  Dr.  Black,  in  1757,  under  the  name  of  fixed 
air.     This  philosopher  proved  that  limestone  and  magne- 
sian  rocks  contained  a  large  quantity  of  this  gas  in  a  stato 
of  solid  combination  with  the  earths,  and  also  that  it  was 
freely  given  out  in  the  processes  of  fermentation,  respira- 
tion, and  combustion. 

367.  Preparation. — Carbonic  acid  is  easily  procured  by 

treating  any  car- 
bonate with  a  di- 
lute acid.  Car- 
bonate of  lime,  in 
the  form  of  mar- 
ble powder,  is 
usually  employed 
for  this  purpose :  it 
is  put  with  a  little 
water  into  a  two- 
mouthed  bottle  A, 
(fig.  270 ;)  dilute 
chlorohydric  acid 
is  turned  in  at  the 
tube-funnel  bt 
when  the  gas  is 


Fig.  270. 


What  is  lamp-black?  365.  What  of  the  compounds  of  C  with 
hydrogen,  Ac.?  366.  What  is  C0a?  What  was  Black's  discovery? 
?67.  How  is  C03  prepared? 


CARBON.  221 

set  free  with  effervescence,  and  escapes  through  the  bent  tube 
at  a.  Its  weight  enables  us  to  collect  it  in  dry  bottles,  by 
displacement  of  air,  as  in  the  case  of  chlorine.  It  may 
also  be  collected  over  water.  No  heat  is  required,  and 
the  acid  is  added  in  small  successive  portions,  the  gas  being 
freely  evolved  at  each  addition.  When  obtained  by  the 
action  of  monohydrated  nitric  acid  on  bicarbonate  of  am- 
monia, the  carbonic  acid  evolved  retains  a  cloudy  appear- 
ance, even  after  passing  through  water,  which  renders  it 
visible — a  point  of  some  importance  in  experiments  with 
this  gas. 

368.  Properties. — At  the  common  temperature  and  pres- 
sure, carbonic  acid  is  a  colorless,  transparent  gas,  with  a 
pungent  and  rather  pleasant  taste  and  odor.  At  a  tem- 
perature of  32°,  and  a  pressure  of  30  to  36  atmospheres,  it  is 
condensed  into  a  clear  limpid  liquid,  not  as  heavy  as  water, 
which  freezes  by  its  own  evaporation  into  a  white,  snow-like 
substance.  We  have  already  described  (151)  the  apparatus 
and  process  by  which  this  interesting  experiment  is  per- 
formed. Carbonic  acid  is  about  once  and  a  half  as  heavy 
as  common  air,  having  a  specific  gravity  of  1-529  ;  and  100 
cubic  inches  therefore  weigh  47-26  grains.  Owing  to  its 
weight,  it  may  be  poured  from  one 
vessel  to  another,  (fig.  271.)  Car- 
bonic acid  instantly  extinguishes 
a  burning  taper  lowered  into  it, 
even  when  mingled  with  twice 
or  three  times  its  bulk  of  air. 
Burning  sulphur  and  phosphorus 
are  also  immediately  extinguished 
in  this  gas.  Potassium,  however, 
quite  clean,  may  be  burned  in  a 
Florence  flask  filled  with  dried 
carbonic  acid;  the  potassium  is 
ignited  by  application  of  heat,  and 
Fis-  2n-  the  carbon  is  then  deposited  on 

the  glass  vessel.  Fresh  lime-water  agitated  with  this  gas, 
rapidly  absorbs  it,  becoming  at  the  same  time  milky,  from 
the  production  of  the  insoluble  carbonate  of  lime;  soluble, 
however,  in  excess  of  carbonic  acid.  In  this  way  the  pre- 
368.  What  its  properties?  What  its  density  ?  How  does  it  affect  eom- 
bustion  ?  How  is  it  decomposed  ? 


222  NON-METALLIC   ELEMENTS 

sence  of  carbonic  acid  in  the  atmosphere  is  easily  detected, 
and  this  gas  is  distinguished  from  nitrogen  by  the  same 
test. 

369.  Cold  water  recently  boiled  absorbs  rather  more  than 
its  own  volume  of   carbonic  acid    gas,  but  with  pressure 
more  will  be   taken  up,  in  quantity  exactly  proportioned 
to  the  pressure  exerted.     The  solution  has  a  pleasant  acid 
taste,  and   temporarily  reddens   blue   litmus   paper.     The 
"soda  water,"  so  much  used  as  a  beverage,  is  usually  only 
water  strongly  impregnated    with  carbonic  acid,  the  soda 
being  generally  omitted  in  its  preparation.     The  efferves- 
cence of  this,  as  well  as  of  small  beer  and  sparkling  wines, 
is  due   to   the  escape  of  this   gas.     Natural    waters    have 
usually  more  or  less  of  this  gas  dissolved  in  them ;  and  some 
mineral  springs,  like  the  Saratoga  and   Ballston  springs, 
and   the  Seltzer  water,  are  highly  charged  with  carbonic 
acid. 

370.  DeatJi  follows  the  inspiration  of  carbonic    acid, 
even  when  largely  diluted  with  air.     It  kills  by  a  specific 
poisonous  influence  on  the  system,  resembling  some  narco- 
tics,  and   is   unlike   nitrogen    in    this   particular,    which 
kills  only  by  exclusion  of  air.      Instances  of  death  from 
sleeping  in  a  close  room  where  a  charcoal  fire  is  burning,  and 
from  descending  into  wells  which  contain  carbonic  acid,  are 
lamentably  frequent.      The  latter  accident  may  be  avoided 
by  taking  the  obvious  precaution  to  lower  a  burning  candle 
into  the  well  before  going  into  it,  when  if  the  candle  burns 
with  undiminished  flame,  all  may  be  considered  safe,  but 
its   being  extinguished  is  certain  evidence  that  the  well  is 
unsafe.     Wells  containing  carbonic  acid  may  often  be  freed 
from  it  by  lowering  a  pan  of  recently-heated  charcoal  into 
the  well,  which  will  soon  absorb  thirty-five  times  its  bulk 
of  this  gas,  (363,)  thus  removing  the  evil.      Even  so  small 
a  quantity  of  carbonic  acid  as  1  or  2  per  cent,  produces,  after 
eome   time,  grave   effects  on  respiration.     Small   animals 
thrown  into  a  vessel  full  of  this  gas,  may  be  recovered  by  im- 
mersion in  cold  water.     The  so-called  Black  Hole  of  Calcutta 
is  a  noted  instance  of  the  fatal  effects  of  respiring  an  atmo- 
sphere overcharged  with  carbonic  acid. 

369.  What  of  its  solution  in  water?  370.  What  is  its  effect  on  life  ? 
Where  do  accidents  often  happen?  How  prevented?  What  quantity 
is  injurious  ? 


CARBON. 


223 


371.  Numerous  natural  sources  evolve  large  quantities  of 
carbonic  acid,  particularly  in  volcanic  districts.     The  Grotto 
del  Cane,  in  Italy,  (dog's  grotto,)  is  a  well-known  example 
of  the  natural  occurrence  of  this  gas.     But  the  quantity 
evolved  there  is  trifling  compared  to  that,  which  escapes 
constantly  from  Lake  Solfatara,  near  Tivoli,  whose  surface  is 
violently  agitated  with  the  gases  boiling  through  it. 

It  is  always  present  in  the  air,  being  given  off  by  the 
respiration  of  all  animals;  and,  besides  the  other  sources 
already  named,  is  an  invariable  product  of  all  common 
cases  of  combustion. 

All  the  carbon  which  plants  secrete  in  the  process  of 
their  development,  is  derived  either  from  the  carbonic  acid 
of  the  atmosphere,  which  they  decompose  by  the  aid  of 
sunlight  and  their  green  leaves,  retaining  the  carbon  and 
returning  the  pure  oxygen  to  the  air;  or  it  is  absorbed  by 
their  rootlets,  and  then  decomposed  by  the  sun's  light  at  the 
surface  of  the  leaf. 

372.  Carbonic  acid  is  formed  of  equal  volumes  of  its 
two  constituent  gases,  condensed  into  one.     For  this  rea- 
son the   air  suffers  no  change  of  bulk  from  the  enormous 
quantities  of  this  gas  which  are  hourly  formed  and  decom- 
posed on  the  earth.      This  acid  unites  with  alkaline  bases, 
forming  an  important  class  of  salts,  (the  carbonates,)  which 
are  decomposed  by  even  the  vegetable  acids,  with  the  escape 
of  carbonic  acid. 

373.  Carbonic    Oxyd,   CO. — Preparation.  —  Tjhls  )gas 
is   most   easily 

obtained  from 
oxalic  acid. 
This  acid,  when 
treated  with 
five  or  six  times 
its  volume  of 
sulphuric  acid, 
in  the  flask  a, 
(fig.  272),  is 
decomposed, 
yielding  equal 
volumes  of  car- 


Fig.  272. 


371.  What  sources  are  named  for  it?  How  in  the  air?  Whence  the  car- 
bon of  plants  ?  372.  What  is  its  constitution  ?  What  are  its  salts  called  ? 
373.  How  is  CO  prepared?  What  of  oxalic  acid  ?  ' 


224  NON-METALLIC   ELEMENTS. 

bonic  acid  and  carbonic  oxyd.  Thus,  C303+HO=COa+CO, 
the  water  remaining  with  the  sulphuric  acid.  The  carbonic 
acid  is  easily  removed  by  a  solution  of  caustic  potash  in  the 
wash-bottle  o.  Dry,  finely-powdered,  yellow  prussiate  of 
potash,  when  decomposed  by  ten  times  its  weight  of  sulphuric 
acid,  in  a  very  capacious  vessel,  yields  an  abundant  volume 
of  pure  oxyd  of  carbon. 

374.  Properties. — This  is  a  colorless,  almost  inodorous 
gas,  burning  with  a  beautiful  pale-blue  flame,  such  as  is 
often  seen  on  a  freshly-fed  anthracite  fire.  Its  specific  gravity 
is  a  little  less  than  that  of  air,  or  -967 ;  and  100  cubic 
inches  of  it  weigh  30-20  grains.     Water  absorbs  about  J9 
of  its  volume  of  itj  it  does  not  render  lime-water  milky, 
and  explodes  feebly  with  oxygen.     It  is  not  respirable,  but 
is  even  more  poisonous  than  carbonic  acid,  producing  a 
state  of  the  system  resembling  profound  apoplexy.     This 
gas  is  very  largely  produced  in  the  process  of  reducing  iron 
from  its  ores  in  the  high  furnace. 

Carbonic  oxyd  is  formed  of  half  a  volume  of  oxygen, 
and  one  volume  of  carbon,  or  two  volumes  of  carbon  and 
one  of  oxygen,  condensed  into  two  volumes. 

375.  Chloro-carbonic  oxyd  is  formed  of  equal  volumes  of 
chlorine  and  oxyd  of  carbon.     This  union  with  chlorine  is 
produced  by  the  influence  of  light,  and  hence  the  product 
was  called  phosgene  gas.   This  is  a  pungent,  highly  odorous, 
suffocating  body,  possessing  acid  properties,  and  decomposed 
by  water.     Its  formula  is  CO.C1,  or  carbonic  acid  in  which 
chlorine  occupies  the   place    of  an  atom  of  oxygen.      Its 
density  is  3407. 

Compounds  of  Carbon  with  the  CJilorine  Group. 

The  chlorids  of  carbon  will  be  described  in  the  organic 
chemistry. 

376.  Bisulphuret   of  Carbon,    C.Sa. — This    remarkable 
product    is   formed  by  the    direct  union    of  its  elements. 
In  a  retort  of  fire-clay  C,  (fig.  273,)  fragments  of  charcoal 
are  placed.     A  porcelain   tube  b   descends    nearly  to  the 
bottom  of  the  retort,  being  luted  with  clay  at  a.     Whon 
the  retort  is  red  hot,  small  bits  of  roll  sulphur  are  from 


374.  What  are  the^  properties  of  CO  ?     375.  What  is  chloro-carbonic 
oxyd  ?    376.  How  is  bisulphuret  of  carbon  prepared  in  fig.  273  ? 


CARBON. 


225 


Fig.  273. 


Fig.  274. 


time  to  time  dropped  in  at  6,  and 
this  orifice  immediately  closed  by 
a  cork.  The  vapor  of  sulphur  rising 
among;  the  ignited  carbon  combines 
with  it,  and  bisulphuret  of  carbon 
distills,  is  con- 
densed by  a 
refrigerating 
tube,(fig.274,) 
and  collected 
in  the  bottle 
surrounded  by 
cold  water,  o. 
The  first  pro- 
duct is  yellow,  from  free  sulphur,  and  is 
purified  by  a  second  distillation.  When 
pure,  bisulphuret  of  carbon  isacolorless, 
very  mobile  and  volatile  fluid,  with  a 
disgusting  odor,  altogether  peculiar.  Its 
density  at  32°  is  1-293  ;  at  60°,  1-271. 
It  boils  at  110°,  and  its  vapor  has  a 
density  of  2-68.  Its  power  of  refracting  light  is  very  remark- 
able. It  dissolves  sulphur,  phosphorus,  and  iodine,  these  bodies 
being  deposited  again  in  beautiful  crystals  by  the  evapora- 
tion of  the  sulphuret  of  carbon.  Gutta  percha  and  India- 
rubber  are  also  soluble  in  it.  It  burns  in  the  air  at  about 
600°,  with  a  pale  blue  flame,  producing  carbonic  and  sul- 
phurous acids.  It  forms  an  explosive  mixture  with  oxygen, 
and  a  combustible  one  with  binoxyd  of  nitrogen.  It  dis- 
solves easily  in  alcohol  and  ether,  and  is  precipitated  again 
by  water. 

Carbon  with  Nitrogen. 

377.  Cyanogen,  C3N  or  Cy. — This  important  and  in- 
teresting compound  of  carbon  and  nitrogen  belongs  appro- 
priately to  the  organic  chemistry ;  but  it  deports  itself  so 
much  like  an  elementary  substance  and  its  compound  with 
hydrogen,  (cyanhydric  or  prussic  acid,)  and  its  metallic 
compounds  also,  are  of  so  much  general  interest,  that  it  is 
proper  to  mention  this  compound-radical  here. 

What  are  its  properties?  What  its  solvent  powers?  377.  What. of 
cyanogen  ?  Give  its  formula. 

16 


226  NON-METALLIC   ELEMENTS. 

Carbon  and  nitrogen  combine  only  indirectly.  If  car- 
bonate of  potassa  and  carbon  are  heated  together  in  a  por- 
celain tube,  while  nitrogen  is  passing  over  them,  oxyd  of 
carbon  escapes,  and  cyanid  of  potassium  in  considerable 
quantity  remains  in  the  tube,  and  may  be  dissolved  out  by 
water.  Cyanogen  is  usually  prepared  in  the  laboratory,  by 
decomposing  cyanid  of  mercury  (CyHg)  in  a  small  retort 
by  heat,  and  collecting  the  gas  over  mercury.  It  is  more 
economically  and  abundantly  prepared,  however,  by  heating 
a  mixture  of  6  parts  of  dried  ferrocyanid  of  potassium,  and 
9  parts  of  bichlorid  of  mercury  in  a  flask  of  hard  glass.  The 
cyanid  of  mercury  formed  is  decomposed  immediately  into 
mercury  and  cyanogen. 

378.  Properties. — Cyanogen  is  a  colorless  gas,  of  a  strong 
and  remarkable  odor,  resembling  peach-pits.  Its  density 
is  1-86.  At  a  temperature  of  — 4°,  it  is  liquefied,  and  at 
common  temperatures,  with  a  pressure  of  4  or  5  atmo- 
spheres. Liquid  cyanogen  is  a  colorless,  very  mobile  fluid, 
whose  density  is  about  0-9.  By  keeping  a  short  time,  it 
undergoes  a  change,  becomes  brown,  and  deposits  a  brown 
powder  in  the  glass.  This  is  paracyanogen,  an  isomeric 
form  of  cyanogen,  a  portion  of  which  is  always  seen  as  a 
residue  in  the  retort  after  decomposing  cyanid  of  mercury. 

Cyanogen  burns  with  a  magnificent  and  characteristic 
purple  flame,  giving  carbonic  acid  and  free  nitrogen.  For 
this  purpose  a  large  vessel  may  be  filled  with  the  gas,  by 
displacement.  Water  dissolves  4  or  5  times  its  volume  of 
cyanogen,  and  alcohol  24  or  25  times  its  volume.  Cyanogen 
forms  cyanids — compounds  almost  exactly  analogous  to  the 
chlorids  of  the  same  metals,  and  in  which  cyanogen  com- 
ports itself  like  an  element. 

Cyanogen  is  formed  from  1  volume  of  carbon  vapor,  weighing  0-8290 
and  1  volume  of  nitrogen  "        0-9713 

1-8003 

which  is  a  close  approximation  to  1-86,  the  result  of  ex- 
periment. 

How  do  C  and  N  unite  ?  How  is  Cy  usually  prepared  ?  How  from 
bichlorid  of  mercury  and  ferrocyanid  of  potassium  ?  378.  What  are  its 
properties  ?  How  liquefied  ?  How  does  the  liquid  change  ?  How  does 
Cy  burn  ?  What  compounds  does  it  form  ?  Analogous  to  what  ?  What 
is  its  volume  composition  ? 


SILICON.  227 


SILICON. 

Equivalent.  21-3.     Symbol,  Si.     Density  in  vapor,  (hypo- 
thetical,} 15-29. 

379.  Silicon  combined  with  oxygen,  forming  silica,  is 
abundantly  distributed  throughout  the  earth.     It  is  said  to 
form  £th  part  of  the  crust  of  the  globe. 

Silicon  is  prepared  by  decomposing  the  double  fluorid  of 
silicon  and  potassium  by  metallic  potas- 
sium. The  potassium,  in  small  pieces, 
is  mingled  with  £th  its  weight  of  the 
dry  white  powder  of  the  double  fluorid, 
in  a  test-tube,  (fig.  275,)  which  is  then 
heated.  Reaction  occurs  as  soon  as 
the  bottom  of  the  tube  is  red,  and 
spreads  through  the  whole  mass.  The 
cool  residue  is  treated  with  water, 
which  dissolves  the  fluorid  of  potas- 
sium, and  leaves  silicon.  Thus, 

3KF.2SiF3-f  6K  =  9KF+2Si. 

380.  Properties. — Silicon  is  a  nut-brown  powder,  and  a 
non-conductor  of  electricity.  Heated  in  air  or  oxygen  it  burns, 
forming  silica.     If  heated  in  a  close  vessel,  it  shrinks,  and 
becomes  more  dense.     Before  ignition  it  is  soluble  in  hydro- 
fluoric acid,  but  after  this  it  is  insoluble,  and  is  incombustible 
in  the  air  or  oxygen  gas.     It  seems  then  to  resemble  the 
graphite  variety  of  carbon.     These  two  diverse  conditions 
of  silicon  are  probably  connected  with  the  two  states  in  which 
silica  occurs. 

381.  Silicic  acid,  or  silica,  Si03,  is  far  the  most  import- 
ant of  all  the  compounds  of  silicon.     It  exists  abundantly 
in  nature,  in  the  form  of  rock  crystal,  agate,  common  un- 
crystallized  quartz,  silicious  sand,  &c. ;  it  also  enters  largely 
into  combination  with  other  substances  to  form  the  rock 
masses  of  the  globe.     It  is  a  very  hard  substance,  easily 
scratching  glass,  and  is  difficult  to  reduce  to  a  powder ;  its 
specific  gravity  is  2 -66.   Its  usual  crystalline  form  (fig.  276)  is 
a  six-sided  prism,  with  two  similar  pyramids.    It  is  infusible 

379.  What  of  silicon  ?  Give  its  equivalent.  How  is  it  prepared  ?  Give 
the  reaction.  380.  What  are  its  properties?  What  two  States?  381. 
What  is  silica? 


228  NON-METALLIC   ELEMENTS. 

alone,  except  by  the  power  of  the  compound  blow- 
pipe. It  dissolves  with  effervescence  in  fluohydric 
acid  and  in  fused  carbonate  of  soda  or  potash.  No 
acid,  except  the  hydrofluoric,  has  any  effect  on  silica. 
When  in  its  finest  state  of  division  it  is  still  harsh 
Fig.  276.  and  gritty  to  the  touch  or  between  the  teeth. 

382.  When  silica  is  fused  in  4  or  6  times  its  weight  of  car- 
bonate of  soda  or  potassa,  and  this  mass  is  treated  with  a 
large  volume  of  dilute  chlorohydric  acid  until  it  manifests  a 
decidedly  acid  reaction,  the  silica  after  some  time  separates 
as  a  transparent,  tremulous  jelly.     This  is  soluble  hydrated 
silica.     If  dried,  it  again  becomes  gritty  and  insoluble  as 
before.     Most  natural  waters  contain  some  small  portion  of 
soluble  silica;  it  has  often  been  seen  in  this  state  in  mines; 
and  on  breaking  open  silicious  pebbles,  the  central  parts  are 
sometimes  semifluid  and  gelatinous.     The  hot  waters  of  the 
great  geysers  in  Iceland,  and  of  other  hot  springs,  also  dis- 
solve large  quantities  of  silica,  probably  aided  by  alkaline 
matter.     Agates,  chalcedony,  carnelian,  onyx,  and  similar 
modifications  of  silica  have  been  deposited  from  the  soluble 
state.     It  is  in  this  condition,  no  doubt,  that  silica  enters 
the  substance  of  many  vegetables,  as,  for  instance,  the  reeds 
and  grasses,  which  have  often  a  thick  crust  of  silica  on  their 
bark.     It  is  in  this  form  also  that  silica  acts  as  the  agent  of 
petrifaction. 

383.  The  acid  powers  of  silica  are  seen  only  at  high  tem- 
peratures, when  it  saturates  the  most  powerful  alkalies  and 
displaces  other  acids,  forming  silicates.  Hence  its  great  use  in 
the  art  of  glass-making,  as  it  is  the  basis  of  all  vitreous 
fabrics,  including  porcelain  and  potters'  ware,  which  are  all 
silicates.     Soluble  glass  is  formed  when  an  excess  of  alkali 
is  employed;  and  liquor  of  flints  is  an  old  term  applied  to  a 
solution  of  silicate  of  potassa  or  soda. 

384.  Chlorine,  bromine,  fluorine,  and  sulphur,  all  form 
compounds  with  silicon,  having  the  formula  SiR3,  or  exactly 
the  formula  for  silica.     The  chlorid  of  silicon  is  formed  by 
passing  dry  chlorine  over  a  mixture  of  fine  silicious  sand 
and  charcoal  in  a  porcelain  tube  heated  to  redness.     It  is  a 
colorless,  mobile  liquid,  having  a  density  of  1-52,  and  boil- 
ing at  138°.     It  is  decomposed  by  water  into  silica  and 

What  its  forms  in  nature  ?  382.  When  fused  with  alkali,  how  is  it 
separated  ?  How  does  it  exist  in  water  and  plants  ?  383.  What  of  it* 
acid  powers  ?  384.  What  does  S  form  with  class  II  ?  What  of  ita  chlorid  ? 


BORON.  229 

ehlorohydri  j  acid.     Bromid  of  silicon  is  formed  in  a  similar 
manner. 

385.  Fluorid  of  Silicon,  (flno-silicic  acid,')  may  be  pre- 
pared by  heating  sulphuric  acid  with  fluor-spar  in  powder,  to 
which  is  added  twice  its  own  weight  of  fine  silica  or  powdered 
glass.     The  apparatus  should  be  quite  dry : 

Fluor-spar.     Silica.  Sul.  Acid.  Sul.  Lime.       Water.  Flue-rid  Silicon. 

3CaF  -f  SiO,  -f  3(SO,.HO)  =  3(CaO.SO,)  -f  3HO  +  SiF,. 

Fluorid  of  silicon  is  a  colorless  gas,  irrespirable,  and  de- 
composed by  water.  Its  density  is  3-57.  It  forms  dense 
white  vapors  in  contact  with  the  moisture  of  the  air.  Passed 
into  water  it  is  immediately  decomposed,  gelatinous  silica  is 
precipitated,  and  the  water  becomes  a  solution  of  hydro-fluo- 
silicic  acid.  The  reaction  is 

3SiF3-f  3HO  =  3HF.2SiF3-f  Si03. 

The  fluorid  of  silicon  should  not  pass  directly  into  the 
water  from  the  gas  tube,  but 
into  some  mercury  on  which 
the  water  rests,  as  in  fig. 
277.  If  this  precaution  be 
neglected  the  open  end  of 
the  gas  tube  will  become 
plugged  with  deposited  sili- 
ca. The  silica  obtained  in 
this  operation,  when  well 
washed,  is  quite  pure.  The 
hydro-fluosilicic  acid  forms 
an  insoluble  salt  with  potas- 
sium 3KF.2SiF3.  Fig.  277. 

BORON. 

Equivalent,  10'90.     Symbol,  B.    Density  in  vapor,  (hypo- 
thetical,} -751. 

386.  Boron  is  known  chiefly  by  its  compounds,  borax  and 
boracic  acid.     Boracic  acid  is  found  in  nature,  either  free 
or  combined  with  various  bases  ',  but  it  is  rather  a  rare  sub- 
stance.    Boron  is  prepared  by  heating  the  double  fluorid  of 

385.  What  is  its  fluorid  ?  Give  the  reaction  by  which  it  is  produced  ? 
What  its  characters  ?  How  does  water  affect  it  ?  What  is  hydro-fluosili- 
cic acid  ?  Explain  its  production  as  in  fig.  277.  386.  What  is  boron  ? 
How  distributed  in  nature  ?  What  its  equivalent  ? 


230  NON-METALLIC   ELEMENTS. 

boron  and  potassium  in  an  iron  vessel,  with  potassium,  an 
in  case  of  silicon.  Boron  is  a  dark  olive-green  powder. 
Heated  to  600°  in  air  it  burns  brilliantly,  forming  boracic 
acid.  It  does  not  conduct  electricity,  and  is  insoluble  in 
water.  Heated  out  of  contact  of  air  it  suffers  no  change. 

387.  Boracic  Acid,  B03,  is  exhaled  from  volcanic  vents, 
as  in  Yulcano,  one  of  the  Lipari  Islands,  and  also  more 
abundantly  in  the  Tuscan  maremma,  not  far  from  Leghorn. 
There  it  issues,  accompanied  by  jets  of  steam,  from  the  soil. 
These  jets  have  been  carried  into  lagoons  of  water  constructed 
around  them,  where  the  boracic  acid  is  taken  up  by  the 
water.  The  heat  of  the  earth  affords  the  means  of  evapo- 
rating the  water.  Figure  278  shows  one  of  these  masonry 
basins,  0,  built  around  the  jets,  (stvjffbni.)  A  series  of 
these,  four  or  five  in  number,  are  arranged  one  above  the 
other :  the  least  concentrated  solutions  occupy  the  upper 
basin,  and  are  in  turn,  once  in  twenty-four  hours,  drawn  off 
to  the  lower,  and  finally  to  the  evaporating  pans  E  F,  also 
heated  by  the  escaping  steam  from  the  earth.  In  this  man- 
ner the  solution  is  brought  to  crystallize,  and  is  purified  by 
repeated  crystallization.  The  production  of  boracic  acid  from 
this  source  equals  two  millions  and  a  half  pounds  per  year. 


Fig.  278. 

388.  In  the  laboratory,  boracic  acid  is  obtained  by  de- 
composing borax  of  commerce.  For  this  purpose,  one  part 
of  borax  is  dissolved  in  two  and  a  half  parts  of  boiling  water, 
and  chlorohydric  acid  added  until  the  liquid  is  strongly  acid. 
On  cooling,  the  boracic  acid  crystallizes  in  elegant  tufts  of 
scaly  crystals,  and  is  purified  by  a  second  crystallization. 
Boracic  acid  is  a  white  pearly  substance  in  thin  scales  :  these 
have  a  feeling  like  spermaceti,  are  feebly  acid  to  the  taste, 
and  soluble  in  twelve  parts  of  boiling  and  in  fifty  parts  of 

387.  How  is  B03  found?  Describe  the  Tuscany  lagoons.  How  are 
they  heated?  Whence  the  B03?  388.  How  is  BO,  prepared  in  the 
laboratory  ?  What  are  its  properties  ? 


HYDROGEN.  %  231 

cold  water.  A  boiling  saturated  solution  deposits  f  ths  of  its 
acid  on  cooling.  The  crystals  contain  43  per  cent,  of  water. 
•By  heat  it  fuses  in  its  crystallization-water,  which  is  finally 
expelled,  and  the  acid,  when  heated  to  redness,  fuses  to  a 
clear  glass,  which  may  be  drawn  out  in  fine  threads.  This 
glassy  acid  loses  its  transparency  by  keeping  for  some  time. 
Boracic  acid  is  a  feeble  acid  in  solution,  but  it  expels  sul- 
phuric acid  from  the  sulphates  at  a  red  heat  and  forms  glass 
with  oxyds  of  lead  and  bismuth,  of  very  high  refractive 
powers.  Alcohol  dissolves  boracic  acid,  and  the  solution, 
when  set  on  fire,  burns  with  a  peculiar  green  flame,  charac- 
teristic of  boracic  acid.  Hydrous  boracic  acid  is  volatile  by 
vapor  of  water,  but  the  glassy  acid  is  quite  fixed  at  the 
highest  temperatures.  Borac'ic  acid  and  the  borates  are 
much  used  as  fluxes,  to  promote  the  fusion  of  other  bodies. 

389.  Chlorid  of  Boron,  BC13,  is  formed  in  the  same  man- 
ner as  chlorid  of  silicon.     It  is  a  colorless  gas  of  a  specific 
gravity  of  4-09,  decomposed  by  water  into  chlorohydric  and 
boracic  acids. 

390.  Fluorid  of  Boron,  BF3. — This  gas  is  obtained  when 
we  heat  together  2  parts  of  fluor-spar  and  1  part  of  fused 
boracic  acid  in  a  vessel  of  porcelain  at  redness.     7B03-f- 
3CaF=3(Ca02B03)-|-BF3.     It  is  a  colorless,  suffocating 
gas,  strongly  acid,  very  soluble  in  water,  and  exceedingly 
greedy  of  it,  so  that  it  even  carbonizes  organic  substances  to 
obtain  it,  in  the  manner  of  sulphuric  acid.     Water  dissolves 
700  or  800  times  its  volume  of  this  gas. 

If  fluor-spar,  boracic  acid,  and  concentrated  sulphuric 
acid  are  heated  together  in  a  glass  retort,  a  gas  of  a  brownish 
color,  very  acid,  and  breaking  on  the  air  in  white  fumes,  ia 
obtained :  this  is  hydro-fluoboracic  acid.  It  must  be  collected 
over  mercury. 

CLASS  VI. 

HYDROGEN. 
Equivalent,  1.      Symbol,  H.     Density,  0-0692. 

391.  History. — Hydrogen  was  first  described  as  a   dis- 
tinct substance  by  the  English  chemist  Cavendish,  in  1766, 
and  was  called  by  him  inflammable  air.     It  had  previously 

What  dissolves  it?  What  is  characteristic  of  BO,?  How  does  heat 
affect  it  ?  389.  What  of  BC1,  ?  390.  What  of  fluorid  of  boron  ?  What 
of  its  properties  ?  391.  What  is  the  history  of  hydrogen  ?  Its  equivalent? 


232 


NON-METALLIC   ELEMENTS. 


been  confounded  with  other  combustible  gases,  several  of 
•which  had  been  long  known.  Hydrogen  exists  abundantly 
in  nature  as  a  constituent  of  water,  and  also  of  nearly  all 
animal  and  vegetable  substances,  in  such  proportions  as  to 
form  water  when  these  bodies  are  burned.  It  is  named 
from  the  Greek  hudor,  water,  and  yennao,  I  form. 

392.  Preparation. — This  gas  is  generally  prepared  by 
the  action  of  dilute  sulphuric  acid  on  zinc  or  iron.  Zinc  ia 
usually  preferred.  The  acid  is  diluted  with  four  or  five 
times  its  bulk  of  water,  and  the  operation  may  be  conducted 


Fig.  279. 

in  a  glass  retort,  or  more   conveniently  by  using  a  gas- 
bottle  a,  (fig.  279,)  containing  the  zinc  in  small  fragments, 
to  which  the  dilute  acid  is  turned  through  the  tube-funnel 
6.     The  shorter  tube  /,  with  a  flexible  joint,  conveys  the 
gas  to  the  air-jar  standing  in  the  cistern  g.     No  heat  is  re- 
quired in  this  operation.     An  ounce  of 
zinc  yields  615  cubic  inches  of  hydro- 
gen gas.     Zinc  is  readily  granulated, 
by  being  turned,  when  melted,  into 
cold  water.     When    hydrogen   is  re- 
quired in  large  quantity,  a  leaden  pot 
or  stone  jar,  properly  fitted,  and  hold-- 
Fig. 280.  jng  a  ga]ion  or  more,  is  used  to  contain 
the  requisite  charge  of  materials,  and  the  gas  is  stored  for 
use  in  a  gas-holder,  or  India-rubber  bag,  (fig.  280,)  (281.) 
393.     The  reaction  in  this  case  is  between  the  zinc  and 


How  does  it  exist  ?    392.  How  is  it  prepared  and  stored  ?    393.  What 
Is  the  reaction  ? 


HYDROGEN.  283 

the  sulphuric  acid,  the  hydrogen  of  the  latter  being  replaced 
by  the  zinc,  thus  :  S03.HO-j-Zn  ==  S03.ZnO+H. 
If  chlorohydric  acid  had  been  used,  the  reaction  is  still  more 
simple,   thus:  HCl-f  Zn  r=ZnCl-j-H. 

Water  is  essential  to  the  rapidity  of  the  action,  by  dissofv 
ing  the  sulphate  of  zinc,  which  is  insoluble  in  strong  sulphu- 
ric  acid,  and  unless  removed,  immediately  arrests  the  process. 

394.  Hydrogen  gas, 
when    obtained    from 
iron,  has  a  peculiar  and 
offensive  odor,  due  to 
the  presence  of  a  vola- 
tile  oil   formed    from 
the  carbon  always  pre- 
sent in  iron.    That  pro- 
cured    from    zinc     is 
also  somewhat  impure. 
Traces  of  sulphuretted 

11  i          i        « 

hydrogen  and  carbonic 
acid  are  usually  found  in  hydrogen,  from  impurity  in  the 
metals  employed ;  and  also  a  trace  of  both  iron  and  zinc  is 
raised  in  vapor,  and  gives  color  to  the  flame  of  common 
hydrogen.  Most  of  these  impurities  are  removed  by  pass- 
ing the  gas  through  a  second  bottle  d,  (fig.  281,)  containing 
an  alcoholic  solution  of  caustic  potash.  Water  only,  in  d, 
removes  the  vapor  of  acid  found  usually  in  the  gas. 

395.  Properties. — Hydrogen  is  a  colorless,  inflammable 
gas  :  it  has  never  been  liquefied.     It  refracts  light  very  pow- 
erfully, and  has  the  highest  capacity  for  heat  of  any  known 
gas.     It  is,  when  quite  pure,  inodorous  and  tasteless,  and 
may  be  breathed  without  inconvenience  when  mingled  with 
a  large  quantity  of  common  air.     The  voice  of  a  person  who 
has  breathed  it  acquires  for  a  time  a  peculiar  shrill  squeak. 
It  cannot,  however,  support  respiration  alone,  and  an  animal 
plunged  in  it  soon  dies  from  want  of  oxygen.     Water  ab- 
sorbs only  about  one  and  a  half  per  cent,  of  its  bulk  of  pure 
hydrogen   gas.     Sounds  are  propagated  in  hydrogen  with 
but  little  more  power  than  in  a  vacuum. 

Hydrogen  is  the  lightest  of  all  known  forms  of  matter, 


How  is  water  necessary  to  it  ?  394.  What  renders  it  impure  ?  How 
is  it  purified  ?  395.  What  are  the  properties  of  hydrogen  ?  How  as  re- 
spects  respiration  ? 


234  NON-METALLIC  ELEMENTS. 

being  sixteen  times  lighter  than  oxygen,  and  fourteen  times 
and  a  half  lighter  than  common  air.  100  cubic  inches  of  it 
weigh  only  2-14  grains.  Soap-bubbles  blown  with  it  rise 
rapidly  in  the  air ;  and  it  is  often  employed  to  fill  balloons 
in  absence  of  the  cheaper  coal  gas.  A  turkey's  crop,  well 
cleansed,  makes  a  good  balloon  on  a  small  scale,  for  the 
class-room,  and  very  beautiful  small  balloons  (from  l£  to  5 
feet  diameter)  are  prepared  in  Paris  of  gold-beaters'  skin. 

396.  Hydrogen  is  the  most  attenuated  as  well  as  the 
lightest  form  of  matter  with  which  we  are  acquainted.  We 
have  reason  to  suppose  the  molecules  of  this  body  to  be 
smaller  than  those  of  any  other  now  known  to  us.  Dr. 
Faraday,  in  his  attempts  to  liquefy  hydrogen,  found  that  it 
would  leak  freely  with  a  pressure  of  27  or  28  atmospheres, 
through  stopcocks  that  were  perfectly  tight  with  nitrogen 
at  50  or  60  atmospheres.  This  extreme  tenuity,  together 
with  the  remarkable  law  of  diffusion  of  gases 
already  explained,  (147,)  renders  it  unsafe  to 
keep  this  gas  in  any  but  perfectly  tight  ves- 
sels. A  small  crack  in  a  bell-jar,  quite  too 
narrow  to  leak  with  water,  will  soon  render 
the  hydrogen  with  which  it  may  be  filled  ex- 
plosive. The  superiority  in  diffusive  power 
which  hydrogen  has  over  common  air,  is  well 
seen  in  what  is  called  Mr.  Graham's  diffusion 
tube,  of  which  a  figure  is  annexed.  A  glass 
tube,  11  or  12  inches  long,  (fig.  282,)  and  of 
convenient  size,  has  a  tight  plug  of  dry  plaster 
of  Paris  at  the  upper  end,  and  being  filled 
with  dry  hydrogen  by  displacement  of  air,  and 
its  lower  end  put  into  a  glass  of  water,  the 
hydrogen  escapes  so  ra>idly  through  the  plaster  plug,  that 
the  water  is  seen  to  rise  in  the  tube,  so  as  in  a  few  mo- 
ments to  replace  a  considerable  portion  of  the  hydrogen,  and 
the  remaining  portion  of  gas  is  found  to  be  explosive. 
Hydrogen  also  enters  into  combination  in  a  smaller  propor- 
tionate weight  than  any  known  body,  (238,)  and  consequent- 
ly has  been  chosen  as  the  unit  of  the  scale  of  equivalents. 


What  of  its  density  ?  What  the  weight  of  100  cubic  inches  ?  What 
use  is  made  of  its  levity  ?  396.  What  is  the  tenuity  of  hydrogen  ?  Give 
illustrations  from  Faraday  ?  What  is  Graham's  diffusion  tube  ?  What 
of  the  atomic  weight  of  hydrogen  ?  Why  has  it  been  adopted  as  unity  ? 


HYDROGEN.  235 

897.  Hydrogen  is  a  most  eminently  combustible  gas,  tak- 
ing  fire  from  a  lighted  taper,  which  is  instantly  extinguished 
by  being  plunged  into  the  gas.  It  burns  with  a  bluish-white 
flame  and  a  very  faint  light.  A  dr}  bottle  with  its  mouth 
downward  (fig.  283)  is  well  suited  to  collect  this  gas  by  dis- 
placement of  air,  as  the  heavier  gases  are  collected 
by  the  reverse  position.  When  lighted,  the  gas 
burns  quietly  at  the  mouth  of  the  bottle;  and 
the  extinguished  taper  may  be  relighted  by  the 
flame  at  the  mouth.  If  the  bottle  is  suddenly  re- 
versed after  the  gas  has  burned  awhile,  the  remain- 
ing gas,  being  mixed  with  common  air,  will  burn 
rapidly  with  a  slight  explosion.  Three  of  the  most 
remarkable  properties  of  hydrogen  are  thus  shown 
by  one  experiment,  viz.  its  extreme  levity,  its 
combustibility,  and  its  explosive  union  with  oxygen. 
If  this  gas  is  incautiously  mingled  with  common 
air,  or  much  more,  with  pure  oxygen,  a  severe  ex- 
plosion results  when  the  mixture  is  fired.  The  ^ 
eyes  or  limbs  of  inexperienced  operators  have  thus  too  often 
paid  the  forfeit  of  carelessness  by  the  explosion  of  glass  ves- 
sels. Particular  caution  is  required  not 
to  employ  any  gas  until  all  the  common 
air  is  expelled,  as  well  from  the  gene- 
rator, as  from  the  receiving-vessel  or  gas- 
holder. 

398.  Water  is  the  sole  product  of  the 
combustion  of  hydrogen.  The  production 
of  water  from  this  combustion,  and  cer- 
tain musical  tones,  are  neatly  shown  by 
an  arrangement  like  fig.  284.  The  gas  is 
generated  in  the  bottle  a,  and  a  perforated 
cork  at  the  mouth  has  a  small  glass  tube, 
from  the  narrow  end  of  which  the  stream 
of  hydrogen  is  lighted.  An  open  glass  tube 
IS'  '  b,  about  two  feet  long,  held  over  this  flame, 
is  at  once  bedewed  by  the  water  produced  in  the 
combustion,  and  a  musical  tone  is  also  generally 
heard.  This  arises  from  the  interruption  which  the 
flame  suffers  from  the  rapid  current  of  air  ascending  Flg*  285' 

397.  Give  illustrations  of  its  combustibility.  What  happens  if  it  ia 
mixed  with  air?  What  caution  is  required?  398.  What  is  the  product 
of  its  combustion  ?  What  happens  if  it  is  burned  from  a  jet  in  a  tube  ? 


236  NON-METALLIC   ELEMENTS. 

through  the  tube,  causing  it  to  flicker,  and  being  moment- 
arily extinguished,  there  occur  a  series  of  little  explosions, 
so  rapid  as  to  give  a  tone.  The  pitch  of  the  note  produced, 
depends  on  the  length  and  size  of  the  glass  chimney  (fig. 
285)  and  the  size  of  the  jet  of  hydrogen,  which  should  bo 
small.  If  the  jet  is  fitted  to  the  gas-holder,  we  can  modulate 
the  tone  by  regulating  the  supply  of  gas  with  the  stopcock. 
The  little  gas  bottle  (fig.  284)  is  often  called  the  "  philoso- 
pher's lamp." 

Compounds  of  Hydrogen  with  Oxygen. 

399.  There  are  two  known  compounds  of  hydrogen  with 
oxygen,  viz. : 

Water  (the  oxyd  of  hydrogen) HO 

Binoxyd  of  hydrogen H0« 

The  first  of  these  is  the  most  remarkable  compound  known, 
whether  we  contemplate  it  in  its  purely  chemical  relations, 
or  in  reference  to  the  wants  of  man  and  the  present  condition 
of  the  globe. 

400.  Water. — The  student  has  already  become  familiar 
with  the  composition  of  water,  as  formed  by  the  union  of 
two  volumes  of  hydrogen  and  one  of  oxygen.     In  examining 
the   compounds  of  hydrogen   and   oxygen,  as  in  all  other 
chemical  investigations,  we  can  pursue  the  subject  either 
analytically  or  synthetically ;  that  is,  we  can  either  form  the 
compounds  by  the  direct  union  of  the  elements,  or  we  can 
decompose  these  compounds,  and  thus  gain  a  knowledge  of 
their  constitution. 

The  simplest  case  of  the  decomposition  of  water  is  that 
where  metallic  potassium,  or  sodium,  is  employed.  The 
P°tassium>  fr°m  its  great  affinity  for  oxygen, 
takes  it  from  the  water,  (fig.  286,)  and  the 
hydrogen  escaping,  is  burned.  If  sodium  is 
introduced  into  an  inverted  test-tube  under 
water,  the  hydrogen  is  collected.  The  reac- 
tion is  K+ HO  =  KO+  H. 

401.  The  voltaic  decomposition  of  water  (224)  is,  however, 
by  far  the  most  satisfactory  experiment  to  this  point  which 

How  is  this  explained?  399.  What  compounds  does  hydrogen  form 
with  oxygen  ?  400.  What  of  the  constitution  of  water  ?  What  is  the 
simplest  case  of  its  decomposition  ?  Hew  does  potassium  effect  this  ? 


COMPOUNDS  OF  HYDROGEN. 


237 


we  possess,  since  both  'ele- 
ments of  the  water  are 
evolved  in  a  pure  form 
and  in  exact  atomic  pro- 
portions by  volume  and 
weight,  (fig.  287.)  In  fact, 
this  is  a  complete  experi- 
mentum  crucis,  being  both 
analysis  and  synthesis;  for 
•fwe  may  so  arrange  the 
single  tube  apparatus  (fig. 
288)  that  the  mixed  gases 
Fig.  287.  from  the  electrolysis  of 
water  may  be  fired  by  an  electric  spark, 
as  soon  as  a  sufficient  volume  of  the 
mixture  has  been  collected.  A  complete 
absorption  follows  the  explosion,  and  ri&*  288> 

the  gases  again  go  on  collecting.  Platinum,  heated  very 
hot,  decomposes  water,  and  both  gases  are  evolved:  this 
happens  when  vapor  of  water  is  passed  through  a  tube  of 
platinum  heated  .to  intense  whiteness. 

402.  What  potassium  and  sodium  accomplish  at  ordinary 
temperatures,  is  accomplished  by  iron,  only  at  a  red  heat. 
The  experiment  figured  in  fig.  289  was  devised  by  Lavoisier : 
an  iron  tube,  (as  a  gun- 
barrel,)  or  better  a  tube 
of  porcelain,  protected  by 
an  exterior  tube  of  iron, 
heated  in  a  furnace  to  full 
redness.  The  tube  contains  \ 
clean  turnings  of  iron,  or 
better  a  bundle  of  clean 
iron  wire  of  known  weight. 
A  small  retort  a,  holding  a  Fig.  289. 

Iktle  water,  is  boiled  by  a  spirit-lamp  at  the  moment  when  the 
tube  is  at  a  full  red-heat :  the  vapor  of  the  water  coming  into 
contact  with  the  heated  iron  is  decomposed,  the  oxygen  is 
retained  by  the  iron,  forming  oxyd  of  iron,  and  the  hydro- 
gen is  given  off  from  the  tube  /,  which  may  be  made  to 
conduct  it  to  the  pneumatic  trough.  For  every  eight 

401.  What  of  the  voltaic  decomposition  of  water  ?  How  does  platinum 
decompose  water  ?  402.  Describe  Lavoisier's  experiment,  fig.  289.  What 
becomes  of  the  oxygen  ? 


238  NON-METALLIC   ELEMENTS. 

grains  of  weight  acquired  by  the  iron,  46  cubic  inches  of 
hydrogen,  weighing  one  grain,  have  been  evolved. 

403.  The  iron  in  this  case  is  evidently  substituted  for  the 
hydrogen,  taking  its  place  with  the  oxygen  to  form  the  oxyd 
of  iron,  while  the  hydrogen  is  set  free.     The  oxyd  of  iron 
resulting  from  this  action,  is  the  same  black  oxyd  which  the 
smith  strikes  off  in  scales  under  the  hammer,  being  a  mix- 
ture of  protoxyd  and  peroxyd.     This  case  of  affinity  is  an 
interesting  one,  because  it  is  seemingly  reversed  when,  under 
the  same  circumstances,  we  pass  a  stream  of  hydrogen  over 
oxyd  of  iron.    The  iron  is  then  reduced  to  the  metallic  state, 
and  water  is  produced.    It  will  be  remembered  that  we  cited 
this  instance  (270)  while  speaking  of  the  influence  of  quantity 
of  matter  in  determining  the  nature  of  the  chemical  changes 
which  might  take  place  among  bodies. 

Referring  to  the  case  (393)  of  sulphuric  or  chlorohydric 
acids  and  zinc,  we  cannot  fail  to  observe  the  similarity  of 
the  two  cases  of  decomposition.  That  water,  or  the  oxyda- 
tion  of  a  base,  is  not  essential  to  the  evolution  of  hydrogen 
is  conclusively  shown  in  the  case  of  dry  chlorohydric  acid 
(HC1)  and  zinc,  which  evolve  hydrogen,  when  no  compound 
containing  oxygen  is  present:  HCl-{-Zn  — ZnCl-|-H. 

404.  Zinc  and  iron  do  decompose  water  even  without  the 
aid  of  an  acid,  but  only  with  great  slowness,  and  the  action 
ceases  as  soon  as  the  metal  is  covered  by  the  coating  of  the 
oxyd  thus  formed,  which  protects  it  from  further  corrosion. 
A  dilute  acid  removes  this  coating  of  oxyd,  and  also  aids, 
no  doubt,  in  establishing  such  electrical  relations  as  to  make 
the  zinc  highly  electro-positive.     That  this  is  the  fact  seems 
quite  probable,  because  pure  zinc  is  hardly  affected  by  dilute 
acids,  and  we  have  already  noticed  the  effects  of  amalgama- 
tion (191)  in  rendering  the  zinc  incapable  of  decomposing 
water. 

Much  mystery  formerly  hung  over  this  case  of  chemical 
action,  which,  is  quite  cleared  away  by  the  view  now  pre- 
sented. It  was  formerly  said  that  the  presence  of  an  acid 
in  water  with  zinc  disposed  the  zinc  to  decompose  the  water. 
This  is  what  was  meant  by  "  disposing  affinity ."  But  there 
can  be  no  oxyd  of  zinc  to  exert  this  influence  on  the  acid, 

403.  What  is  the  theory  of  the  process?  Why  is  this  an  interesting 
case  of  affinity  ?  What  similarity  is  noticed  with  a  previous  case  ?  404. 
What  of  the  slow  decomposition  of  water  by  zinc  ?  What  view  was  held 
formerly?  What  of  disposing  affinity? 


COMPOUNDS  OF  HYDROGEN.  239 

until  the  water  is  decomposed ;  so  that  the  idea  that  the 
acid  disposed  the  zinc  to  decompose  the  water  is  quite  futile. 

405.  The  real  nature  of  hydrogen  was  for  a  long  time 
not  well  understood.     It  was  associated  with  oxygen  and 
chlorine,  because  it  was  supposed  to  bear  the  same  relations 
to  chlorohydric  acid,  that  oxygen  bears  to  sulphuric  and 
chloric  acids.    It  is  now  known  that  hydrogen  is  most  closely 
allied  to  the  metals,  particularly  to  zinc  and  copper;  that 
the  chlorids,  iodids,  and  fluorids  of  hydrogen,  although  they 
possess  the  characters  which  we  assign  to  acids,  resemble  in 
many  respects  the  chlorids,  iodids,  &c.,  of  the  same  metals; 
that  in  fact,  hydrogen  is  a  metal  exceedingly  volatile,  proba- 
bly standing  in  that  respect  in  the  same  relation  to  mercury, 
that  mercury  does  to  platinum,  but  still  possessed  of  all  truly 
chemical  peculiarities  of  the  metallic  state,  and  no  more 
deprived  of  the  commonplace  qualities  of  lustre,  hardness, 
or  brilliancy,  than  is  the  mercurial  atmosphere  which  fills  the 
apparently  empty  space  in  the  barometer  tube.     (Dr.  Kane.) 
The  vapor  of  mercury,  and  of  other  volatile  metals,  is,  like 
hydrogen,  a  non-conductor  of  heat  and  electricity;  but  we 
cannot  on  this  account  deny  their  metallic  character.     We 
must  not  forget,  moreover,  that  hydrogen  may  yet,  by  suffi- 
cient cold  and  pressure,  be  made  fluid  or  solid,  when  doubt- 
less we  shall  see  its  resemblance  in  physical,  as  well  as  we 
now  do  in  chemical  characters,  to  the  metals.    The  propriety 
of  assigning  to  hydrogen  the  place  in  our  classification  which 
it  occupies,  will  thus  be  more  apparent  to  those  who  have 
usually  seen  it  placed  next  to  oxygen. 

406.  'A  mixture  of  oxygen  and  hydrogen  gases  will  never 
unite  under  ordinary  circumstances  of  temperature  and  pres- 
sure ;  but  the  passage  of  an  electric  spark  through  them,  or 
the  application  of  red-hot  flame,  or  an  intensely  heated  wire, 
will  produce  an  explosive  union,  destructive  to  the  contain 
ing  vessel,  unless  the  gas  is  in  extremely  small  quantities. 
The  re-composition  or  synthesis  of  water,  was  proved  in  the 
experiment  in  the-single  cell  decomposing  apparatus,  (fig. 
288.)    If  that  explosion  had  taken  place  in  a  dry  vessel  over 
mercury,  the  interior  would  have  been  bedewed  with  moisture 
from  the  regenerated  water.     This  may  be  done,  as  in  fig. 

405.  What  is  said  of  the  real  nature  of  hydrogen  ?  What  reasons  exist 
for  supposing  it  a  metal  ?  406.  How  is  the  union  of  hydrogen  and  oxygon 
effected  ? 


240 


NON-METALLIC   ELEMENTS. 


290,  where  a  strong  glass  tube 
t  is  divided  into  equal  parts, 
for  convenience  of  measuring, 
and  supported  firmly  in  the 
mercury  vase  v.  An  electrical 
spark  from  the  Leyden  vial  I  is 
made  to  pass  through  the  gas- 
eous mixture  by  means  of  the 
platinum  wires  p  soldered  into 
the  walls  of  the  upper  part  of 
the  tube.  Such  an  arrange- 
ment is  an  eudiometer,  some 
allusion  to  which  was  made  in 
332.  Hydrogen  furnishes  us 
the  most  convenient  means  of 
analysis  of  gases  containing 
oxygen,  by  combining  with  it 
to  form  water.  In  eudiometri- 
cal  analysis  it  is  always  from 
the  volume  that  the  result  of 
the  analysis  is  deduced,  and  not, 
as  in  case  of  solids,  from  the 
weight.  A  very  good  form  of  eudiometrical  tube  is  that  of 
Dr.  Ure,  (fig.  291.)  It  is  a  graduated  tube,  closed  as  before 
at  one  end,  and  bent  on  itself.  When  used, 
it  is  filled  with  dry  mercury,  by  placing 
it  horizontally  in  the  mercury  trough.  A 
portion  of  the  gaseous  mixture  to  be  de- 
tonated is  then  introduced,  the  thumb 
placed  over  the  open  end,  and  all  the  mix- 
ture adroitly  transferred  to  the  closed  limb. 
The  mercury  is  made  to  stand  at  the  same 
level  in  both  limbs,  by  forcing  out  a  por- 
tion with  a  glass  rod  thrust  in  at  the  full 
side.  These  adjustments  being  made,  the 
whole  bulk  of  the  mixture  is  read  on  the 
graduation,  and  while  the  thumb  is  firmly 
held  over  the  open  end  of  the  tube,  an 
electrical  spark  is  made  to  explode  the 
Fig.  291.  gases.  The  air  between  the  thumb  and 


Describe  fig.  290.    How  is  hydrogen  useful  in  gas  analysis  ?    What  U 
Ure's  eudiometer?    How  is  it  used? 


COMPOUNDS   OP   HYDROGEN.  241 

the  mercury  acts  like  a  spring  to  break  the  force  of  the  ex- 
plosion •  and  afterward,  on  removing  the  thumb,  the  weight 
of  the  atmosphere  forces  the  mercury  into  the  shorter  leg, 
to  supply  the  partial  vacuum  occasioned  by  the  union  of  the 
gases.  Proper  allowances  being  made  for  temperature  and 
pressure,  the  quantity  of  residual  gas  is  read  on  the  gradua- 
tion, and  a  calculation  can  then  be  made  of  the  amount  of 
oxygen  present.  If  the  gas  contains  carbon,  carbonic  acid 
would  be  formed,  and  must  be  absorbed  by  potash  solution. 

407.  Yalta's  eudiometer,  represented  in  fig.  292, 
is  a  very  complete  instrument  for  gas  analyses 
over  the  pneumatic-trough.     In  this  instrument 
the  explosion  is  made  in  a  thick  glass  tube  A  B, 
into  which  the  electrical  spark  is  passed  by  t.     The 
graduated  measure  p  screws  into  the  funnel  D,  and 
is  used  to  measure  the  portion  of  gas  to  be  deto- 
nated, which  is  poured  in  by  the  funnel  C  at 
bottom.     Before  use,  the  tube  P  is  removed,  the 
cocks  R  and  S  are  both  opened,  and  the  whole  in- 
strument sunk  in  the  cistern  until  it  is  entirely  full 
of  water.     The  cock  R  is  then  shut,  the  portion 
of  gas  measured  in  P  and  introduced  by  C,  the  cock 
S  closed,  and  explosion  made.     If  any  residue  re- 
mains, its  quantity  is  measured  by  opening  R, 
when  it  rises  into  P,  previously  filled  with  water, 
and  its  quantity  is  read  off  on  the  graduation. 
The  metallic  strap  p  serves  as  a  communication 
for  the  electric  circuit,  and  also  as  a  scale  of  equal 
parts  for  ruder  measurements  of  gas.     This  instru- 
ment is  well  adapted  for  rapid  class  illustration, 
in  the  lecture  room,  and  is  applicable  in  all  eu- 
diometrical  experiments  in  which  gaseous  analysis 
is  to  be  performed  by  oxygen  and  hydrogen.     For 
accurate   research,  the  beautiful    eudiometer  of 
Regnault  is  the  most  reliable  instrument. 

408.  The  explosion  of  oxygen  and  hydrogen  gases,  when 
mingled  in  atomic  proportions,  is  very  severe,  and  can  be 
performed  safely  only  on  very  small  volumes  of  the  gases, 
or  in  strong  vessels  of  metal.     The  ingenuity  of  the  demon- 
strator will  devise  many  instructive  and  amusing  experi- 

llow  is  the  carbonic  acid  removed?    407.  What  is  Volta's  eudiometer? 
How  is  it  used  ?     408.  What  illustrations  are  given  of  the  severity  of  th 
explosion  of  oxygen  and  hydrogen  ? 


242  NON-METALLIC  ELEMENTS. 

ments  depending  on  the  explosion  of  this  mixture.  The 
gas-pistol,  and  hydrogen-gun,  (fig.  293,)  a  blad- 
der filled  and  fired  from  a  pin-hole  or  by  an 
electric  spark,  soap-bubbles,  and  other  familiar 
illustrations,  all  give  evidence  of  the  energy  of 
the  action  by  which  water  is  formed  from  the 
union  of  its  elements.  The  explosion  is  probably 
due  to  the  rush  of  air  consequent  on  the  sudden 
expansion  and  immediate  condensation  of  a  vo- 
Fig.  293.  lume  of  steam  formed  at  the  most  intense  heat 
which  can  be  produced  by  art. 

The  union  of  oxygen  and  hydrogen  can,  however,  be  ef- 
fected slowly  and  quietly,  without  any  explosion  or  visible 
combustion.  This  is  accomplished  by  passing  the  mixed 
gases  through  a  tube  heated  below  redness ;  and  at  a  still 
lower  temperature,  if  the  tube  contains  coarsely  powdered 
glass  or  sand.  We  see  in  this  case  an  instance  of  that  re- 
markable phenomenon  called  "surface  action,"  (251)  be- 
fore alluded  to. 

409.  Professor  Dbbereiner,  of  Jena,  observed,  in  1824, 
that  platinum  in  the  state  of  fine  division,  known  as  spongy 
platinum,  would  cause  an  immediate  union  of  these  gases. 
A  drop  of  strong  chlorid  of  platinum  evaporated  on  writing 
paper,  and  the  paper  burned,  gives  platinum  in  that  state, 
and  such  a  pellet  of  paper  may  be  prepared  in  an  instant 
and  used  to  fire  hydrogen.  The  common  instrument 
employed  for  lighting  tapers  is  made  by  taking  advantage 
of  this  principle.  A  little  spongy  platinum  is  formed  into 
a  ball,  and  mounted  on  a  ring  of  wire  (fig.  294) 
which  slips  within  the  cup  d  on  the  top  of  gas- 
holder a  (fig.  295.)  The  gas  is  generated  by  the 
action  of  dilute  acid  in  the  outer  vessel  a  on  a 
lump  of  zinc  z  hanging  in  the  inner  vessel  /,  and 
Fig.  294.  jg  jej.  ouj.  aj.  pieasure  by  the  cock  c,  issuing  in  a 

stream  on  the  spongy  platinum.  The  latter  is  at  once 
heated  to  redness  by  the  stream  of  hydrogen,  which  is  con- 
densed within  its  pores  to  such  a  degree  that  it  combines 
with  a  portion  of  oxygen,  always  present  in  the  sponge  by 
atmospheric  absorption.  The  union  of  these  gases  is  attended 
by  intense  heat,  and,  as  a  consequence,  the  platinum  at  once 
glows  with  redness,  and  the  hydrogen  is  inflamed.  After 

How  is  this  union  effected  slowly  ?  409.  What  was  the  observation  of 
Dobereiner  ?  Describe  the  hydrogen  lamp  ? 


COMPOUNDS   OF   HYDROGEN. 


243 


some  time  the  sponge  loses  this  property  to 
a  certain  extent,  but  it  is  again  restored  by 
being  well  ignited.  When  the  spongy  pla- 
tinum is  mixed  with  clay  and  sal-ammoniac 
made  into  balls  and  baked,  its  effects  are  less 
intense,  and  such  balls  are  often  used  in  analy- 
sis to  cause  the  gradual  combination  of  gases. 
Faraday  has  shown  that  clean  slips  of  pla- 
tinum foil,  and  even  of  gold  and  palla- 
dium, qan  effect  the  silent  union  of  hydro- 
gen and  oxygen.  For  this  purpose  the  pla- 
tinum is  cleaned  in  hot  sulphuric  acid,  washed 
thoroughly  with  pure  water,  and  hung  in  a  jar 
of  the  mixed  gases.  Combination  then  takes  place  so  ra- 
pidly as  to  cause  at  every  instant  a  sensible  elevation  of  the 
water  in  the  jar.  If  the  metal  is  very  thin,  it  sometimes 
becomes  hot  enough  during  the  process  of  combination  to 
glow,  and  even  to  explode  the  gases. 

410.  The  same  effect  of  platinum  in  causing  combination 
is  seen  in  other  bodies  besides  oxygen  and  hydrogen.  Seve- 
ral mixtures  of  carbon  gases  will  act  with  platinum  in  the 
same  way ;  and  the  vapors  of  alcohol  or  ether 
may  be  oxydized  by  a  coil  of  platinum  wire 
hung  from  a  card  in  a  wineglass  (fig.  296) 
containing  a  few  drops  of  either  of  these 
fluids.  The  coil  of  wire  is  heated  to  red- 
ness in  a  lamp,  and,  while  still  hot,  is  hung 
in  the  glass ;  it  then,  if  air  has  free  access, 
retains  its  red-hot  condition  as  long  as  any 
vapor  of  ether  or  alcohol  remains.  In  this 
case,  only  the  hydrogen  of  the  ether,  or  al- 
cohol, is  oxydized,  and  the  carbon  is  unaf-  Fig.  296. 
fected;  a  peculiar  irritating  acid  vapor  is  given  off,  which 
affects  the  nose  and  eyes  unpleasantly.  Little  balls  of  pla- 
tinum sponge  suspended  over  the  wick  of  an  al- 
cohol lamp  will,  in  like  manner,  glow  for  hours 
after  the  lamp  is  extinguished.  A  spirit-lamp  fed 
with  alcoholic  ether  will  cause  the  coil  of  plati- 
num wire  (fig.  297)  to  glow  for  hours  in  the  same 
way,  constituting  what  has  been  called  the  aphlo- 
gistic  lamp. 

What  has  Faraday  shown  on  this  point  ?     410.  How  does  platinum 
act  on  vapors  ?     What  is  the  aphlogistic  lamp  ? 


244 


NON-METALLIC   ELEMENTS. 


411.  The  oxyliydrogcn  blowpipe  of  Hare  enables  the 
chemist  to  use  safely  the  intense  heat  produced  by  the  com- 
bustion of  oxygen  and  hydrogen.  In  Dr.  Hare's  instru- 
ment the  two  gases  were  brought  from  separate  gas-bolderb 
and  mingled  only  in  the  moment  of  contact.  The  flame  of 
the  oxyhydrogen  blowpipe  differs  from  the  flame  of  a  lamp 
or  candle  by  being,  so  to  speak,  a  cone  of  aerial  matter  en- 
tirely ignited  in  every  part,  while  the  flame  of  a  candle  is 

ignited  only  on  the  outside, 
(460.)  The  structure  of 
the  jet  contrived  by  Profes- 
sor Daniell  illustrates  this, 
where  the  oxygen  tube  o  is 
seen  (figure  298)  to  pass 
through  that  carrying  the  hydrogen,  H.  Thus  the  combus- 
tible gas  is  in  contact  with  the  oxygen  to  burn  it  both  from 
the  air  and  from  the  instrument.  The  jet  may  be  pro- 
vided with  a  cock  (fig.  299)  and  connected  with  the  gas- 
holders by  two  flexible  pipes  attached  at  0  and  H.  The 
o 


Fig.  293. 


Fig.  299. 


Fig.  301. 


Fig.  300. 

gas-holders  may  conveniently  be 
made  of  impervious  caoutchouc  cloth, 
arranged  with  pressure  boards,  and 
weights  as  in  fig.  300,  an  arrange- 
ment which  admits  of  convenient 
transportation  and  dispenses  with 
the  use  of  water.  The  gas  is  ad- 
mitted and  expelled  by  the  flexible 
pipes  p  and  controlled  by  the  cocks  c . 
The  effects  of  the  compound  blow- 
pipe may  also  be  safely  produced 
by  passing  a  stream  of  oxygen  from 
a  gas-holder  (fig.  301)  through  the 


411.  What  is  Hare's  blowpipe  ?   How  does  its  flame  differ  from  common 
flames?    How  is  the  jet  fig.  298  constructed?   How  are  the  gases  disposed  ? 


COMPOUNDS   OF   HYDROGEN.  245 

flame  of  a  spirit-lump  w.     The  jet  is  regulated  by  the  cock 
I,  while  the  lamp-flame  supplies  the  hydrogen. 

412.  The  mixed  gases,  in  atomic  proportions,  are  some- 
times forced  by  a  condensing  syringe  into  a  very   strong 
metallic  box,  from  which  they  issue  by  their 

own  elasticity.  To  prevent  the  danger  of 
explosion,  a  contrivance  is  employed  called 
"  Hemming' s  safety  tube."  This  is  a  brass 
tube,  six  or  eight  inches  long,  filled  with  fine 
brass  wire,  closely  packed,  and  having  a  coni- 
cal rod  of  brass  forcibly  driven  into  their 
centre,  by  which  the  wires  are  very  closely 
crowded  together.  This  forms  in  fact  a  great 
number  of  small  metallic  tubes,  through  which 
the  gas  must  pass.  It  is  a  property  of  such 
small  tubes  entirely  to  arrest  the  progress  of 
flame  as  we  shall  presently  see.  (Safety 
lamp  of  Davy,  464.)  The  jet  is  screwed  to 
one  end  of  this  tube,  and  the  other  end  is 
connected  with  the  holder  of  the  mixed  gases.  Fig.  302. 
Several  severe  explosions,  it  is  said,  have  occurred,  even  with 
all  these  precautions ;  so  that  if  the  mixed  gases  are  used 
at  all,  it  should  only  be  in  a  bag  or  bladder,  the  bursting 
of  which  can  be  attended  with  no  danger. 

413.  The  effects  of   the  compound   blowpipe  are  very 
remarkable.     In  the  heat  of  its  focus  the  most  refractory 
metals  and  earths  are  fused,  or  dissipated  in  vapor.     Plati- 
num, which  does  not  melt  in  the  most  intense  furnace  of  the 
arts,  here  fuses  with  the  rapidity  of  wax,  and  is  even  vola- 
tilized.    Even  those  metallic  oxyds,  as  lime,  magnesia,  and 
alumina,  which  are  entirely  infusible  in  any  other  artificial 
heat,  yield  to  this  focus.     By  the  adroit  management  of  the 
keys,  which  a  little  practice  soon  teaches,  we  can  either  re- 
duce metallic  oxyds,  or  oxydize  substances  still  more  highly. 
The  flame  of  the  mixed  gases  falling  on  a  cylinder  of  pre- 
pared lime,  adjusted  to  the  focus  of  a  parabolic  mirror,  pro- 
duces the  most  intense  artificial  light  known.     This  is  what 
is  called  the  Drummond  light.     It  is  extensively  employed  in 
distant  night-signals,  and  can  be  seen  farther  at  sea  than  any 


412.  How  are  the  mixed  gases  burned  safely?  What  is  Hemming's 
safety  jet  ?  413.  What  are  the  effects  of  the  compound  blowpipe ' 
What  it  the  Drummond  ligLt  ? 


246  NON-METALLIC   ELEMENTS. 

other  light.  It  is  also  used  as  a  substitute  for  the  sun's  light 
in  optical  experiments.  The  galvanic  focus  alone,  among 
artificial  sources  of  light,  surpasses  it;  (200.)* 

History  of  Water. 

414.  "Water,  when  pure,  is  a  colorless,  inodorous,  tasteless 
fluid,  which  conducts  heat  and  electricity  very  imperfectly, 
refracts  light   powerfully,  and  is  almost  incapable  of  com- 
pression.    We  have  already  made  so  much  use  of  water,  in 
illustration  of  the  laws  of  heat  and  of  chemical  combina- 
tion, in   the  former  part  of  this  volume,  that  the   student 
must  already  be  familiar  with  many  of  its  attributes.     Its 
greatest  density,  it  will  be  remembered,  (103,)  is  found  to 
be  at  39°-5,  or,  more  exactly,  39° -83.     It  is  the  standard 
of  comparison  (33),  for  all  densities  of  solids  and  liquids. 
In  the  form  of  ice,  its  density  is  0-94,  and  at  32°  it  freezes. 
One  imperial  gallon  of  water  weighs  70,000  grains,  or  just 
ten   pounds.     The    American    standard    gallon    holds,    at 
39°-83  Fahr.,  58,372  American  troy  grains  of  pure  distilled 
water.     One   cubic   inch,  at  60°  and  30  inches  barometer, 
weighs  252  j40508<j  grains,  which  is  815  times  as  much  as  a  like 
bulk  of  atmospheric  air.      One  hundred  cubic    inches  of 
aqueous  vapor,  at  212°  and  30  inches  barometer,  weigh 
14-96    grains,  and    its    specific  gravity  is  0-622.     Water 
boils  under  ordinary  circumstances  at  212°;  but  we  have 
seen  that  its  boiling  point  was  very  much  affected  by  the 
nature  of  the  vessel.     It  evaporates  at  all  temperatures. 

415.  The  conversion  of  water  into  ice  is  attended  with 

i  *i£feji    ^e    exerc^se  °f  crystallo- 

O       SK  ^S  genie  attractions,  although 

^^  11  II  **$$$*  t,j|C    resulting  forms    are 

Fig.  303.  rarely   visible.       But    in 

snow  we  often  see  beautifully  grouped  compound  crystals, 
resulting  from  the  union  of  forms  derived  from  the  hexago- 
nal prism.  Figure  303  gives  some  of  the  more  simple  of 


414.  What  are  the  properties  of  Tvater  ?  What  the  temperature  of  its 
greatest  density  ?  What  the  density  of  ice  ?  What  that  of  a  cubio 
inch?  of  a  gallon?  of  its  vapor?  415.  What  is  said  of  the  crystalliza- 
tion of  water? 


*  Mr.  E.  N.  Kent,  of  New  York,  furnishes  a  very  efficient  and  cheap  form 
of  compound  blowpipe,  with  gas-bags  and  Drutumond  light  apparatus. 


COMPOUNDS   OF   HYDROGEN. 


247 


these  forms.    The  laws  of  congelation  of  water  have  already 
been  fully  explained,  123. 

416.  Pure  water  is  never  found  on  the  surface  of  the 
earth;  for  the  purest  natural  waters,  evaporated  to  dryness, 
leave  always  a  visible  residue,  containing  small  quantities  of 
earthy  or  saline  matters  which  have  been  dissolved  from  the 
rocks  and  soil.      Moreover,  all  good  water  —  that  which  is 
fit  for  the  use  of  man  —  has  a  considerable  quantity  of  car- 
bonic acid  and  atmospheric  air  dissolved  in  it,  (332,)  and 
without  which  it  would  be  flat  and  unpalatable. 

A  jar  of  spring  water  placed  under  a  bell  on  the 
air-pump  (fig.  304)  will  appear  to  boil  as  the 
exhaustion  proceeds  from  escape  of  the  dissolved 
air.  It  is  upon  this  air  that  the  fish  and  other  water- 
breathing  animals  depend  for  life  ;  and  conse- 
quently, when  a  vessel  containing  fish  is  placed 
on  the  air-pump  and  the  air  exhausted,  the  fish  are 
seen  soon  to  give  signs  of  discomfort,  (fig.  305,) 
and  will  die  if  the  operation  is  continued. 
Many  mineral  springs,  besides  the  saline 
matters  they  hold  in  solution,  are  highly 
charged  with  sulphuretted  hydrogen,  car- 
bonic acid,  and  other  gases  derived  from 
chemical  changes  going  on  in  the  beds 
from  which  they  flow. 

Pure  water  can  be  procured  only  by 
distillation,  and  it  is  a  substance  of  such 
indispensable  importance  to  the  chemist,' 
that  every  well-  furnished  laboratory  is  pro- 
vided with  means  for  its  abundant  prepa- 
ration.  A  copper  still,  well  tinned,  and  connected  with  a 
pure  block-tin  worm  or  condenser,  answers  very  well  to  pro- 
duce the  common  supply.  .  But  very  accurate  operations 
require  it  to  be  again  distilled  in  clean  vessels  of  hard  glass. 

417.  The  solvent  powers  of  water  far  exceed  those  of 
any  other  known  fluid.     Nearly  all  saline  bodies  are,  to  a 
greater  or  less  extent,  dissolved  by  water,  and  heat  generally 
aids  this  result.      In  the  case  of  common   salt,  however, 
and  a  few  other  bodies,  cold  water  dissolves  as  much  as  hot. 

What  depends  on  the  presence  of  air  in  the  water  ?  What  other 
gases  are  found  in  it?  How  is  pure  water  obtained  ?  416.  What  fo- 
reign substances  are  found  in  water?  How  is  the  air  in  water  shown  ? 
Why  important  to  animal  life  ?  417.  What  are  the  solvent  powers  of  water  ? 


305> 


248 


NON-METALLIC   ELEMENTS. 


The  solvent  powers   of  pure   water  are  generally  greater 
than  those  of  common  water. 

Gases  are  nearly  all  absorbed  or  dissolved  in  cold  water, 
and  some  of  them  to  a  very  great  extent,  while  others,  as 
hydrogen  and  common  air,  very  slightly.  Hot  water  dis- 
solves many  bodies  which  are  quite  insoluble  in  cold, 
especially  when  aided  by  small  portions  of  alkaline  matter. 
The  waters  of  the  hot  springs  in  Iceland  and  Arkansas  de- 
posit much  silicious  matter  before  held  in  solution ;  and  Dr. 
Turner  found  that  common  glass  was  dissolved  in  the  cham- 
ber of  a  steam-boiler  at  300°,  and  stalactites  of  silica  were 
formed  from  the  wire  basket  in  which  the  glass  was  sus- 
pended. 

418.  Water  always  absorbs  the  same  volume  of  a  given 
gas,  whatever  may  be  its  density :  thus,  of  carbonic  acid, 
of  ordinary  tension,  it  dissolves  its  own  volume  j  it  would  do 
no  more  if  the  gas  were  reduced  to  half  its  first  density  ;  and 
it  dissolves  the  same  volume  when  the  pressure  is  at  80 
atmospheres.  Hence  water  which  has  absorbed  gases  under 
pressure,  parts  with  them  in  effervescence  when  that  pressure 
is  removed.  Ag.-iin,  if  a  mixture  of  gases  is  present  at  a 
given  tension,  water  absorbs  of  each  the  same  volume  as  it 
would  take  up  if  only  that  one  was  present.  Such,  it  will 
be  remembered,  is  the  fact  with  regard  to  the  gases  of  the 
atmosphere,  (382.)  Gases  dissolved  in  water  are  all  ex- 
pelled by  boiling.  If, 
therefore,  we  would 
know  what-  volume 
of  a  given  gas  was 
dissolved  in  water, 
the  fact  is  accurately 
determined  by  boiling 
a  measured  quantity 
in  a  flask  quite  full, 
as  in  figure  306,  aud 
conveying  the  escap- 
ing gas  by  a  bent  tube 
(also  previously  filled 
with  water)  to  a  gra- 
duated jar  on  the 


Pig.  306. 


What  of  the  action  of  hot  water!'  418.  What  volume  of  gases  does 
water  absorb?  How  does  pressure  affect  this  ?  How  of  mixed  gases  ?  How 
is  the  volume  of  gases  contained  in  water  determined?  Describe  tig.  306. 


COMPOUNDS  OP  HYDROGEN.          249 

mercurial  cistern.     We  then  measure  the  volume  of  gas  ex« 
pelled  directly. 

419.  The  powers  of  water  as  a  chemical  agent  are  very 
various  and  important.     From  its  neutral,  mild,  and  salu- 
tary character,  we  are  accustomed  to  regard  it  only  as  a 
negative  substance,  possessed  of  little  energy,  while  it  is  in 
fact  one  of  the  most  important  chemical  agents  in  our  pos- 
session.    Besides  its  solvent  powers,  we  know  that  it  com- 
bines with  many  substances,  forming  a  large  class  of  hy- 
drates :  hydrate  of  lime  and  potash  are  examples.     It  is 
also,  as  we  have  seen,  (320,)  essential  to  the  acid  properties 
of  common  sulphuric,  phosphoric,  and  nitric  acids,  acting 
here  the  part  of  a  much  more  energetic  base  than  in  the  hy- 
drates.    It  forms  an  essential  part  in  the  composition  of 
many  neutral  salts,  and  can  be  replaced  in  composition  by 
other  neutral  saline  bodies;  while  as  water  of  crystallization 
it  discharges  still  another  important  and  distinct  function, 
the  crystalline  forms  of  many  salts  being  quite  dependent 
on  its  presence  in  atomic  proportions.     Of  organic  struc- 
tures, both  animal  and  vegetable,  it  forms  by  far  the  most 
considerable  constituent.     Its  vapor  at  high  temperatures 
displaces  some  of  the  most  powerful  acids,  as  Tilghmann  has 
shown,  in  his  patent  process  for  procuring  the  alkaline  bases 
by  decomposing  their  sulphates,  chlorids,  and  even,  to  some 
extent,  silicates,  by  vapor  of  water  at  a  high  temperature. 
Sulphate  of  lime,  for  example,  so  treated,  has  all  its  sul- 
phuric acid  driven  off  as  S03,  and  caustic  lime  is  left  behind. 
The  geological  importance  of  these  facts  can  hardly  be  over- 
estimated. 

420.  Peroxyd  or  Binoxyd  of  Hydrogen, — This  curious 
compound  was  discovered  in  1818,  by  M.  Thenard.     It  is 
obtained  in  decomposing  the  peroxyd  of  barium  by  as  much 
very  cold  solution  of  hydrofluoric  acid  (fluosilicic  or  phos- 
phoric acid  may  be  used  as  well)  as  will  exactly  saturate 
the  base,  the  whole  being  precipitated  as  fluorid  of  barium. 
The  reaction  may  be  expressed  thus : 

Poroxyd  of  barium.    Fluohydric  add.    Fluorid  of  barium.    Peroxyd  of  hydrogen. 

Ba02      +        HF       =       BaF       +         H03. 
The  peroxyd  of  hydrogen  remains  dissolved  in  the  water, 
which  is  freed  ,from  the  insoluble  fluorid  of  barium  by  filtra- 

419.  What  are  the  chemical  powers  of  water  ?  What  is  crystallization, 
water  ?  What  are  Tilghmann's  experiments  ?  420.  What  is  tho  per- 
oxyil  of  hydrogen  ?  How  procured  ?  Give  the  reaction. 


ii50  NON-METALLIC   ELEMENTS. 

tion,  and  then  evaporated  in  the  vacuum  of  an  air-pump  by 
the  aid  of  the  absorbing  power  of  sulphuric  acid. 

421.  Properties. — The  properties  of  this  body  are  very 
remarkable.     When  as  free  from  water  as  possible,  it  is  a 
syrupy  liquid,  colorless,  almost  inodorous,  transparent,  and 
possessed  of  a  very  nauseous,  astringent,  and  disgusting  taste. 
Its  specific  gravity  is  1453,  and  no  degree  of  cold  has  ever 
reduced  it  to  the  solid  form.     Heat  decomposes  it  with  effer- 
vescence and  the  escape  of  oxygen  gas.     It  can  be  preserved 
only  at  a  temperature  below  50°.    The  contact  of  carbon  and 
many  metallic  oxyds  decomposes  it,  often  explosively,  and 
with  evolution  of  light.     No  change  is  suffered  by  many 
bodies  which  decompose  it;  but  several  oxyds,  as  those  of 
iron,  tin,  manganese,  and  others,  pass  to  a  higher  state  of 
oxydation.      Oxyd   of  silver,   and  generally  those  oxyds 
which  lose  their  oxygen  at  a  high  temperature,  are  reduced 
to  a  metallic  state  by  this  decomposition.     When  diluted, 
and  especially  when  acidulated,  the  peroxyd  of  hydrogen  is 
more  stable.     It  is  dissolved  by  water  in  all  proportions, 
bleaches  litmus  paper,  and  whitens  the  skin.     None  of  its 
compounds  are  known,  nor  does  it  seem  to  have  any  ten- 
dency to  combine  with  other  bodies. 

Compounds  of  Hydrogen  with  the  II.  and  III.  Classes. 

422.  The  eminently  electro-positive  character  of  hydrogen 
causes   it    to  form  well-characterized  and  analogous  com- 
pounds with  all  the  members  of  the  oxygen  group.     These 
binary  compounds  have  frequently  been  called  the  hydracids, 
in  distinction   from  those  acid  bodies  already  considered, 
which,  in  parity  of  language,  have  been  called  the  oxacids. 

It  is,  however,  more  in  accordance  with  facts  and  the 
principles  of  a  philosophic  classification,  to  look  upon  these 
bodies  as  having  in  reality  the  same  essential  characters  as 
the  chlorids,  bromids,  iodids,  &c.,  of  other  electro-positive 
bases.  The  principles  of  our  nomenclature  require  these 
compounds  to  be  called  after  their  electro-negative  elements, 
t.  e.  chlorohydric  acid,  bromohydric  acid.  Their  general 
formula  is  HR.  The  compounds  of  hydrogen  to  be  con- 
sidered under  this  head  are — 


421.  "What  are  its  properties  ?  422.  What  are  the  hydracids  ?  What 
riew  is  taken  of  their  constitution?  What  compounds  are  enumerated 
under  this  head  ?  What  is  their  general  formula  ? 


COMPOUNDS    OF   HYDROGEN.  251 


Chlorohydric  acid HOI 

Bromohydric  acid HBr 

lodohydric  acid HI 


Sulphydric  acid HS 

Selenhydric  acid HSe 

Tellurhydric  acid HTe 


Fluohydric  acid HF 

423.  Hydrogen    and  chlorine,  mingled  in   the   gaseous 
state,  combine  with  explosion  by  the  touch   of  a   match, 
forming  chlorohydric  acid.     The  rays  of  the  sun  effect  the 
same  result  instantaneously,  while  in  diffuse  light  combina- 
tion follows  in  a  gradual  manner  and  quietly.    In  the  dark, 
no  union  occurs,  showing  that  light  in  this  case  plays  the 
part  of  heat,  and  impresses,  as  we  shall  see,  a  peculiar  con- 
dition on  chlorine.     If  two  vessels  of  equal 

capacity  (fig.  307)  are  filled,  the  one,  A,  with 
dry  hydrogen,  the  other,  B,  with  dry  chlo- 
rine, by  displacement,  and  are  then  united, 
as  seen  in  the  figure,  on  exposing  them  with 
precaution  to  the  sun's  direct  rays,  an  im- 
mediate explosion  follows.  Dr.  Draper  has 
shown  that  chlorine  gas  which  had  been  ex- 
posed alone  and  dry  to  the  sun's  light  ac- 
quired the  power  of  forming  this  explosive 
union  with  hydrogen,  even  in  the  dark,  and 
retained  it  for  some  time;  while,  on  the  other  hand,  chlorine 
prepared  in  the  dark  manifests  no  avidity  for  hydrogen  un- 
less exposed  to  the  light.  This  fact  was  before  mentioned 
(288)  when  speaking  of  the  active  and  passive  conditions 
of  chlorine.  In  its  passive  state,  (as  prepared  in  the  dark,) 
it  actually  replaces  hydrogen  in  the  constitution  of  many 
organic  bodies,  or,  in  other  words,  assumes  an  electro-posi- 
tive condition.  The  effect  of  the  sun's  light  is  to  confer  a 
new  state  upon  it,  probably  by  a  new  arrangement  of  its 
molecules,  by  which  its  character  is  completely  changed. 
It  then  apparently  becomes  highly  electro-negative. 

The  decomposition  of  water  by  chlorine  (288)  evinces  its 
strong  affinity  for  hydrogen.  Chlorine  thus  becomes  one 
of  the  most  powerful  oxydizing  agents  known,  since  the 
nascent  oxygen  given  off  during  the  decomposition  of  water 
attacks  with  energy  any  third  body  which  may  be  present 
that  is  capable  of  combining  with  it. 

424.  Chlorohydric  Acid,  HC1.— If  the  experiment  (fig. 

423.  How  do  chlorine  and  hydrogen  act  when  mingled  ?  Describe 
fig.  307.  What  has  Draper  shown  ?  What  is  the  passive  state  of  chlo- 
rine ?  What  relation  has  it  in  this  state  to  organic  bodies  ?  On  what 
dues  the  decomposition  of  water  by  chlorine  depend  ? 


252  NON-METALLIC  ELEMENTS. 

307)  is  placed  in  diffuse  light,  the  green  color  of  the  gas  is 
seen  gradually  to  diminish  and  finally  to  disappear  alto- 
gether; and,  on  opening  the  junction  beneath  mercury,  no  ab- 
sorption occurs,  and  the  vessels  are  found  to  be  filled  with 
chlorohydric  acid  gas.  It  appears  therefore  that  this  acid  is 
formed  by  the  union  of  equal  volumes  of  the  constituent  gases 
without  condensation  Its  density  is  consequently  equal  to 
half  the  sum  of  the  united  densities  of  chlorine  and  hydro- 
gen, i.e.244+  -069=2-509  -f-2  =  1-254,  theoretical  den- 
sity of  chlorohydric  acid  gas.  Experiment  gives  1-2474. 

425.  Chlorohydric  acid  is  a  colorless,  acid,  irrespirable 
gas.     It  forms  copious  clouds  of  acid  vapor  with  the  moist- 
ure of  the  air,  very  suffocating,  and  irritating  the  eyes.     It 
extinguishes  a  lighted  candle,  and  is  not  decomposed  by 
electricity.     It  is  very  soluble  in  water,  which  at  32°  takes 
up  about  500  times  its  volume  and  acquires  a  density  of 
1-21.    At  a  higher  temperature  it  absorbs  less.     This  gas  is 
therefore  collected  over  mercury.     A  bit  of  ice  passed  up 
to  a  jar  of  it  on  the  mercury  cistern,  is  fused  immediately 
by  its  avidity  for  water,  a  dilute  solution  of  chlorohydrio 
acid  results,  and  the  mercury  rises  to  fill  the  jar.     With  a 
pressure  of  over  26  atmospheres  it  becomes  a  colorless  liquid, 
which  has  never  been  frozen. 

426.  Preparation. — For  experimental  purposes  in   the 
laboratory  it  is  sufficient  to  warm  the  wtrong  commercial 
liquid  acid,  which  parts  with  a  large  portion  of  gas  at  a  gentle 

heat.  This  may  be  dried 
by  passing  it  through  a 
chlorid  of  calcium  tube. 
The  apparatus  thus  ai- 
ranged  is  shown  in  figure 
308.  The  concentrated 
acid  is  placed  in  c  and  its 
moisture  is  removed  by 
-the  chlorid  of  calcium 
apparatus  a.  The  weight 
Fi»-  308-  of  the  gas  enables  us  to 

collect  it  by  displacement  of  air  in  dry  vessels  b.  For 
this  purpose  it  is  not  usually  requisite  to  dry  it. 

In  the  arts  it  is  always  obtained  from  the  decomposition 

424.  What  is  the  constitution  of  chlorohydric  acid?  What  is  its  theo- 
retical composition  and  density  ?  Its  experimental  ?  425.  What  are  its 
properties  ?  How  soluble  in  water  ?  How  collected  ?  426.  How  is  it 
pi-epared  for  experiment  in  the  laboratory  ?  Describe  fig.  308. 


COMPOUNDS   OF   HYDROGEN. 


253 


of  common  salt,  (chlorid  of  sodium,  NaCl,)  by  sulphuric 
acid.  The  reaction  is  sufficiently  simple  :  NaCl  -f-  S03. 
HO  =  (NaO.S03)  -f  HC1.  The  apparatus  employed  in 
this  process  is  shown  in 
fig.  309.  Common  salt 
is  placed  in  the  flask  a, 
provided  with  a  safety 
tube  /  and  an  eduction 
tube  I.  The  sulphuric 
acid  for  decomposing  the 
salt  is  introduced  at 
pleasure  through  f.  The 
action  is  aided  by  a  gen- 
tle heat  from  the  fur- 
nace below.  The  chloro- 
hydric  acid  is  rapidly 
evolved  and  passes  into 
c,  where  it  is  washed  by 
a  little  warm  water  and 
thence  by  e  to  the  last  ^ 
bottle  dj  where  it  is  ab-  \ 
sorbed  by  the  ice-cold 
water  which  it  contains. 
In  the  middle  bottle  is 
a  tube  g,  of  large  size 
and  open  at  both  ends, 

its  lower  extremity  dips  into  the  wash-water.  This 
contrivance  prevents  the  accident  which  is  otherwise 
likely  to  happen  should  a  partial  vacuum  occur  in  a, 
from  a  cessation  of  the  action ;  when  the  pressure 
of  the  air  on  the  fluid  in  d  would  carry  it  back  into 
c,  and  finally  into  a.  The  safety  tube  (fig.  310)  at- 
tached to  the  flask  a  also  serves  to  prevent  this  acci- 
dent as  well  as  to  introduce  the  acid.  When  a  liquid 
is  poured  in  at  the  funnel-top,  it  must  rise  as 
high  as  the  turn,  "before  it  can  pass  down  into  the 
flask,  and  a  portion  of  the  fluid  is  therefore  always 
left  behind  in  the  bend,  which  serves  as  a  valve 
against  the  entrance  of  air,  and  also  effectually  pre- 
vents an  explosion  of  the  flask  in  case  the  tube  of  . 
delivery  should  become  stopped.  This  simple  con- Flg'310* 

How  is  it  procured  in  the  arts  ?    Give  the  reaction.    Describe  the  appa^ 
rntus,  fig.  309.    What  is  a  safety  tube  ?    Describe  fig.  310. 


Fig.  309. 


254 


NON-METALLIC   ELEMENTS. 


trivance  we  have  often  employed  but  have  not  before  ex« 
plained  its  action.  This  same  apparatus  may  be  employed  in 
making  solutions  of  all  the  absorbable  gases,  and  is  so  simple 
as  to  be  within  the  means  of  the  humblest  laboratory ;  the 
essential  parts  being  only  wide-mouthed  bottles,  glass  tubes, 
a  gas  bottle  or  flask,  and  corks. 

427.  Pure  chlorohydric  acid  is  procured  by  distilling  the 
commercial  acid.  The  distilling  apparatus  employed  for 
this  purpose  is  seen  in  fig.  311.  The  heat  is  applied  by  a 
sand-bath  beneath  the  retort.  The  gas  given  off  is  absorbed 
by  a  little  water  placed  in  the  last  bottle,  which  is  connected 
by  a  bent  tube  with  the  two-necked  receiver.  If  the  com- 


Fig.  311. 

mercial  acid  is  diluted  by  water  until  it  has  the  specific  gra- 
vity I'll,  it  no  longer  evolves  acid  fumes  when  heated,  and 
the  fluid  distilled  has  the  same  density  as  that  in  the  retort, 
retaining  16  equivalents  of  water. 

428.  Properties. — Liquid  chlorohydric  acid  is  a  colorless, 
highly  acid,  fuming  liquid,  having  when  saturated  a  speciBc 
gravity  of  1'247  :  it  then  contains  42  parts  in  a  hundred  of 
real  acid.  Its  purity  is  tested  by  its  leaving  no  residue  on 
evaporating  a  drop  or  two  on  clean  platinum,  and  by  its 
giving  no  milkiness  when  a  solution  of  chlorid  of  barium  is 
added  to  it,  (due  to  sulphuric  acid.)  Neutralized  by 
ammonia,  it  ought  not  to  become  black  when  hydrosul- 

427.  How  obtained  pure?  Describe  fig.  311.  At  what  density  does  it 
distill  unchanged?  428.  What  are  the  properties  of  the  liquid  acid? 
What  ars  tests  of  its  purity  ? 


COMPOUNDS   OP   HYDROGEN.  255 

phuret  of  ammonium  is  added,  (due  to  iron.)  This  acid  is 
an  electrolyte,  and  is  also  decomposed  by  ordinary  elec- 
tricity. A  mixture  of  muriatic  acid  gas  with  oxygen,  passed 
through  a  red-hot  tube,  produces  water  and  chlorine.  The 
commercial  acid  is  always  impure,  and  colored  yellow  by 
free  chlorine,  iron,  and  organic  matters. 

^ests. — A  solution  of  nitrate  of  silver  detects  the  pre- 
sence of  a  soluble  chlorid,  or  of  chlorohydric  a,cid, 
by  forming  with  it  a  whito  curdy  precipitate  of 
chlorid  of  silver,  which  is  soluble  in  ammonia, 
but  insoluble  in  acids  or  water.  A  rod  a,  if  dip- 
ped in  ammonia  and  held  over  a  glass  containing 
chlorohydric  acid,  gives  off  a  dense  white  cloud 
of  chlorid  of  ammonium. 

429.  The  uses  of  chlorohydic  acid  are  very  numerous. 
Its  decomposition  by  oxyd  of  manganese  affords  the  easiest 
mode  of  procuring  chlorine,  (282.)     It  dissolves  a  great 
number  of  metals  and  oxyds,  forming  chlorids,  from  which 
these   metals   may  be  obtained  in  their   lowest   state  of 
oxydation.     In  chemical  analysis  and  the  daily  operations 
of  the  laboratory  it  is  of  indispensable  use. 

Chlorohydric  acid  is  made  in  the  arts  in  immense  quanti- 
ties, especially  in  England,  where  the  carbonate  of  soda  is 
largely  made  from  common  salt  (chlorid  of  sodium)  by 
the  action  of  sulphuric  acid.  Mingled  with  half  its  own 
volume  of  strong  nitric  acid,  it  makes  the  deeply  colored, 
fuming,  and  corrosive  aqua-regia.  This  mixed  acid  evolves 
much  free  chlorine,  which  in  its  nascent  state  has  power  to 
dissolve  gold,  platinum,  &c.,  forming  chlorids  of  those 
metals,  and  not  nitromuriates  as  was  formerly  supposed. 
As  soon  as  all  the  chlorine  is  evolved,  this  peculiar  power 
of  the  aqua-regia  is  lost. 

430.  Bromohydric  Acid,  HBr,  Bromid  of  Hydrogen. — 
Hydrogen  and  bromine  do  not  act  upon  each  other  in  the  gase- 
ous state,  even  by  the  aid  of  the  sun's  light;  but  a  red  heat 
or  the  electric  spark  causes  union — only  among  those  parti- 
cles, however,  which  are  in  immediate  contact  with  the  heat, 
the  action  not  being  general.     Bromohydric  acid  may  be 
prepared  by  the  reaction  of  moist  phosphorus  on  bromine  in 
a  glass  tube  (fig.  313.)    The  gas  given  off  must  be  collected 

What  tests  are  named?  429.  "What  are  its  uses?  What  is  aqua-regia  ? 
430.  What  is  bromohydrie  acid  ?  How  prepared? 


256  NON-METALLIC   ELEMENTS. 

over  mercury.  It  is  composed,  like  chlorohydric  acid,  of 
equal  volumes  of  its  elements  not  condensed.  Its  specific 
gravity  is  2-731,  and  it  is  condensed  by  cold  and  pressure 
into  a  liquid.  In  its  sensible  properties  it  bears  a  close  re- 
semblance to  chlorohydric  acid.  With  the  nitrates  of  silver, 
lead,  and  mercury,  it  gives  white  precipitates  similar  to  the 
chlorids.  It  has  a  strong  avidity  for  water,  and  dissolves 
largely  in  it,  giving  out  much  heat  during  the  absorption. 
The  saturated  aqueous  solution  has  the  same  reactions  as  the 
dry  acid,  and  fumes  with  a  white  cloud  in  contact  with  air. 
It  dissolves  a  large  quantity  of  free  bromine,  acquiring 
thereby  a  red  tint. 

431.  lodohydric  Add. — This  body  may  be  formed   by 
the   direct   union   of   its   elements   at    a  red-heat,  but  is 
more  easily  prepared  by  acting  on  iodine  and  water  with 
phosphorus,  by  which   means   the  gas  is  formed  in   large 
quantities.     The  action  of  phosphorus  and  iodine  is  violent 
and  dangerous,  but  may    be  regulated  and  made   safe  by 
putting  a  little  powdered  glass  between  each  layer  of  phos- 
phorus and  iodine,  (fig.  313.)  Phos- 
phoric acid  is  formed  and  remains  in 
solution,  while  the  iodohydric  acid 
gas  is  given  out,  and  may  be  col- 
lected over  mercury,  or  dissolved 
in  water.     The  dry  gas  has  a  great 
avidity    for    water.      Its    specific 
gravity  is  4443,  being  formed,  like 
the   last  two  compounds,  of  one  vo- 

313  lume  of  each  element  uncondensed. 

Cold  and  pressure  reduce  it  to  a 
clear  liquid,which,at — 60°  Fahr., freezes  into  a  colorless  solid, 
having  fissures  running  through  it  like  ice.  It  forms  a  very 
acid  fluid  by  solution  in  water,  which  has,  when  saturated,  a 
specific  gravity  of  !•?,  and  emits  white  fumes.  The  aqueous 
solution  is  also  prepared  by  transmitting  a  current  of  hydro- 
sulphuric  acid  through  water  in  which  free  iodine  is  sus- 
pended. The  gas  is  decomposed,  sulphur  set  free,  and 
hydriodic  itcid  produced,  which  is  purified  from  free  hydro- 
sulphuric  acid  by  boiling,  and  from  sulphur  by  filtration. 

432.  Properties. — The  aqueous  iodohydric  acid  is  easily 

431.  How  is  iodohydric  acid  prepared?   What  are  its  properties?  How 
to  its  aqueous  solution  prepared  ? 


COMPOUNDS    OP   HYDROGEN.  257 

decomposed  by  exposure  to  the  air,  iodine  being  set  free. 
It  forms  characteristic,  highly  colored  precipitates  with 
most  of  the  metals,  particularly  with  lead,  silver,  and 
mercury.  Bromine  decomposes  it,  and  chlorine  decomposes 
both  hydrobromic  and  hydriodic  acids,  thus  showing  the 
relative  affinities  of  these  bodies  for  hydrogen.  This  acid 
is  a  valuable  reagent;  its  presence  in  solution  is  easily 
detected  by  a  cold  solution  of  starch,  which,  with  a  few 
drops  of  strong  nitric  or  sulphuric  acid,  instantly  gives  the 
fine  characteristic  blue  of  the  iodid  of  starch. 

433.  Fluohydric  acid  is  obtained  from  the  decomposition 
of  fluor-spar  by  strong  sulphuric  acid.  The  operation  must 
be  performed  in  a*  retort  of  pure  lead,  silver,  or  platinum, 
and  requires  a  gentle  heat.  Fig.  814  shows 
'the  form  of  retort  used  for  this  purpose,  the 
junction  of  the  head  and  body  is  made  tight 
by  a  lute  of  gypsum  and  water,  a^ 
as  any  lute  containing  silica 
will  be  attacked  by  the  fluohy- 
dric  acid.  The  sulphate  of 
Fig.  314.  j-me  resuiting  from  the  action 
forms  a  solid  insoluble  mass  in  the  body  of 
the  retort  :  hence  the  necessity  of  so  large  an 
opening.  The  fluohydric  acid  resulting  is 
condensed  in  a  large  tube  of  lead,  bent  as  in  Fig.  315. 
fig.  315,  so  as  to  enter  a  refrigerant  apparatus  :  at  one  end  it 
is  luted  to  the  beak  of  the  retort,  at  the  other  is  narrowed 
to  a  small  aperture.  The  reaction  is  expressed  as  follows  : 


CaF       -f     S03.HO     =     S03.CaO     -f       HF 

The  fluor-spar  employed  should  be  quite  free  from  silica 
and  sulphur. 

434.  Properties.  —  Concentrated  fluohydrie  acid  is  a  gas 
which  at  32°  is  condensed  into  a  colorless  fluid,  with  a  den- 
sity of  1-069.  Its  avidity  for  water  is  extreme,  and  when 
brought  in  contact  with  it,  the  acid  hisses  like  red-hot  iron. 
Its  aqueous  solution,  as  well  as  the  vapor  of  the  acid,  attack 
glass  and  all  compounds  containing  silica  very  powerfully.  It 


482.  What  are  its  characters?  433.  How  is  fluohydric  acid  pre- 
pared ?  Describe  the  apparatus,  fig.  314.  What  is  the  rsaction  ?  434. 
What  are  its  properties  ? 

17 


258  NON-METALLIC   ELEMENTS. 

is  often  used  in  the  laboratory  for  marking  test-bottles  or  gra- 
duated measures,  or  biting  in  designs  traced  in  wax  on  the 
surface  of  glass  plates.  It  is  a  powerful  acid,  with  a  very 
sour  taste,  neutralizes  alkalies,  and  permanently  reddens  blue 
litmus.  On  some  of  the  metals  its  action  is  very  powerful; 
it  unites  explosively  with  potassium,  evolving  heat  and  light. 
It  attacks  and  dissolves,  with  the  evolution  of  hydrogen,  cer- 
tain bodies  which  no  other  acid  can  affect,  such  as  silicon,  zir- 
conium, and  columbium.  Silicic,  titanic,  columbic,  and  mo- 
lybdic  acids  are  also  dissolved  by  it. 

Fluohydric  acid,  in  its  most  concentrated  form,  is  a  most 
dangerous  substance.  It  attacks  all  forms  of  animal  matter 
with  wonderful  energy.  The  smallest  cfrop  of  the  concen- 
trated acid  produces  ulceration  and  death,  when  applied  to 
the  tongue  of  a  dog.  Its  vapor  floating  in  the  air  is  very 
corrosive,  and  should  be  carefully  avoided.  If  it  falls,  even 
in  small  spray,  on  the  skin,  it  produces  an  ulcer,  which  it  is 
very  difficult  to  cure.  For  this  reason  it  is  quite  inexpe- 
dient for  unexperienced  persons  to  attempt  its  preparation. 
By  using  a  weaker  sulphuric  acid,  however,  or  by  having 
water  in  the  condenser,  no  risk  is  incurred.  As  before  re- 
marked, it  attacks  -silica  more  powerfully  than  any  other 
body.  This  fact  puts  us  in  possession  of  an  admirable  mode 
of  analyzing  silicious  minerals,  when  we  do  not  wish  to  fuse 
them  with  an  alkali. 

435.   Sulphydric  Acid,  Sulphuretted  Hydrogen. — When 

the  protosulphuret 
of  iron  or  the  sul- 
phuret  of  antimony 
is  treated  with  a  dilute 
acid,  effervescence 
occurs,  and  a  gas  is 
given  out  having  a 
most  disgusting,  fetid 
odor,  which  at  once 
reminds  us  of  the 
nauseous  smell  of  bad 
eggs.  This  process  is 
performed  in  the  evo- 
lution-bottle A,  (fig. 

What  its  uses?  What  of  its  safety  ?  How  does  it  act  on  the  organs? 
What  is  its  great  affinity  ?  435.  What  is  hydro-sulphuric  acid  ?  What  is 
its  common  name  ? 


COMPOUNDS  OF  HYDROGEN. 


259 


310)  in  which  a  portion  of  sulphuret  of  iron  is  acted  on  by 
dilute  sulphuric  acid  turned  in  at  the  funnel-tube  b.  The  es- 
caping gas  is  led  by  a  to  the  inverted  bottle.  This  operation 
should  be  performed  in  a  well-drawing  flue  or  in  the  open 
The  reaction  is  FeS-fS08-f  HO=FeO.S08+HS. 


air. 


If  sulphuret  of  antimony  is  used,  heat  is  needed;  and  we 
must  employ  the  apparatus  fig.  317,  and  chlorohydric  in- 


Fig.  317. 

stead  of  sulphuric  acid.  This  mode  evolves  no  free  hydro- 
gen, which  is  present  in  small  quantities  when  protosul- 
phuret  of  iron  is  used.  This  is  sulphuretted  hydrogen  gas, 
one  of  the  most  useful  reagents  to  the  chemist,  especially  in 
relation  to  the  metallic  bodies. 

436.  Properties. — Sulphydric  acid  is  a  colorless  gas,  of  a 
disgusting  odor,  like  that  of  putrid  eggs.  Its  density  is 
1-191,  or  a  little  heavier  than  air.  It  is  liquefied  at  50° 
by  a  pressure  of  15  or  16  atmospheres,  and  at  — 122° 
Fahrenheit  it  freezes  into  a  white  confused  crystalline  solid, 
not  transparent,  and  which  is  much  heavier  than  the  fluid, 
sinking  in  it  readily.  Heat  partially  decomposes  it.  It 
burns  with  a  blue  flame,  depositing  sulphur  on  the  interior 
of  the  bottle.  Sulphurous  acid  and  water  are  its  products 
of  combustion.  Mingled  with  1£  volumes  of  oxygen  the 
combustion  is  complete,  no  sulphur  is  deposited,  and  there 

How  prepared  ?  Give  the  reaction.  Why  is  sulphuret  of  antimony 
sometimes  preferred?  436.  What  are  its  properties?  Is  it  combustible  ? 
How  is  it  decomposed  ?  How  much  oxygen  burns  it  ?  What  are  the  pro- 
du-jtg  of  combustion  ? 


260  NON-METALLIC   ELEMENTS. 

is  a  shrill  explosion.  Strong  nitric  acid  also  inflamos  and 
burns  it.  Chlorine,  bromine,  and  iodine  also  decompose  it. 
Mingled  with  a  considerable  volume  of  air  in  contact  with 
organic  matter,  it  slowly  forms  sulphuric  acid.  It  is  a  true 
but  feeble  acid. 

Water,  if  cold,  and  recently  boiled,  dissolves  2$  or  3  times 
its  volume  of  sulphydric  acid.  Woulf 's  apparatus  (fig.  321) 
is  best  adapted  for  this  purpose.  The  solution  has  the 
characteristic  smell  and  taste  of  the  gas  and  all  its  pro- 
perties. If  boiled  it  loses  all  its  gas,  and  if  kept  a  short 
time  it  becomes  troubled  from  precipitation  of  sulphur :  this 
is  due  to  oxygen  dissolved  in  the  water.  The  solution  of 
sulphydric  acid  should  therefore  be  kept  in  well-stopped  bot- 
tles, quite  full.  This  solution  is  much  used  in  the  labora- 
tory. Added  to  solutions  of  metallic  salts 
it  throws  down  characteristic  precipitates, 
offering  to  the  chemist  an  easy  mode  of 
distinguishing  substances  or  of  separating 
them  from  one  another.  The  gas  passed 
directly  into  solutions  of  metals  as  in  fig. 
318,  answers  the  same  purpose.  Such  an 
Fig.  318.  apparatus  is  conveniently  kept  for  use, 

and  should  be  always  at  hand. 

437.  It  occurs  in  nature  in  many  mineral  springs,  giv- 
ing the  water  highly  valuable  medicinal  characters.  Many 
such  springs  in  this  country  are  much  resorted  to,  as  at  Sha- 
ron and  Avon,  N.  Y.,  and  the  sulphur  springs  of  Virginia. 
At  Lake  Solfatara,  near  Home,  this  gas  is  given  off  copi- 
ously with  carbonic  acid.  The  disgust  at  first  felt  at  drink- 
ing  these  nauseous  waters  is  soon  overcome,  and  those  patients 
who  take  them  in  large  quantity  soon  observe  the  gas  to 
penetrate  their  whole  system  and  exude  in  their  perspiration. 
Silver  coin,  and  other  silver  articles  in  the  pockets  of  such 
persons,  are  soon  completely  blackened  by  the  coating  of 
sulphuret  of  silver  formed  on  their  surface. 

Although  salutary  when  taken  into  the  stomach,  it  is, 
even  when  present  in  the  air  in  only  a  small  quantity,  a 
deadly  poison  to  the  more  delicate  animals.  Numerous 
deaths  are  also  recorded  of  those  who  have  attempted  to  work 
in  vaults  and  sewers  where  it  abounds. 

How  soluble  is  it?  Will  the  solution  remain  unchanged?  Why  not? 
437.  What  is  its  natural  history  ?  IIow  does  it  affect  life  ? 


COMPOUNDS  OF  HYDROGEN. 


261 


438.  When  sulphurous 
acid  and  sulphuretted  hy-% 
drogen  gas  are    brought 
together   in    a    common 
receiving  vessel,  mutual 
decomposition       ensues, 
and  the  sulphur  of  both 
is   thrown   down,  which 
attaches  itself  to  the  sides 
of  the  vessel  in  a  thick 
yellow  pellicle.     The  sul- 
phurous acid  is  evolved 
in  a,   (fig.  319,)  (310,) 

and  sulphydric  acic  in  b,  and  both  are  carried  to  the  bottom 

of  the  middle  bottle  at  a  b. 

Sulphydric  acid  is  formed  from  1  volume  of  hydrogen=  0-0692 

And  J  volume  of  sulphuric  vapor6-^2  = 1*1090 

Giving  for  the  theoretical  density  of  the  gas 1/1782 

While  experiment  gives 1*1912 

There  is  a  bisulphydric  acid,  HSa,  but  no  further  men- 
tion will  be  made  of  it. 

439.  Selenhydric  and  tellurhydric  acids  are  exactly  analo- 
gous to  the  last-named  compound,  and  their  general  interest 
is  so  small  that  we  pass  them  without  further  notice. 

Compounds  of  Hydrogen  with  Class  III. 

440.  The  compounds  which  hydrogen  forms  with  the  nitro- 
gen group  are  strongly  contrasted  in  chemical  and  physical 
characters  with  the  remarkable  natural  family  which  has 
just  engaged  our  attention.    The  latter  are  all  acid,  and  gene- 
rally in  an  eminent  degree.     The  compounds  of  hydrogen 
with  the  nitrogen  group  are,  on  the  contrary,  either  neutral 
or  strongly  basic,  forming  a  series  of  salts  or  peculiar  com- 
pounds with  the  hydracids  before  named. 

The  compounds  named  under  this  head  are — 

Ammonia NHj 

Phosphuretted  hydrogen PH, 

We  might  add  in  the  same  connection  the  hydrogen  com- 
pounds of  arsenic  and  antimony,  AsH3  and  SbHu,  sub- 

438.  What  is  the  experiment  in  fig.  319  ?  What  is  the  composition  of 
this  gas?  What  its  theoretical  and  experimental  isnsity?  439.  What 
compounds  are  used  in  this  section  ?  Give  the  ftrmulae.  What  other 
similar  compounds  are  named  ? 


262  NON-METALLIC   ELEMENTS. 

stances  quite  similar  to  PH.,  in  many  of  their  attributes, 
but  convenience  refers  these  to  the  metallic  bodies. 

441.  Or'ujiii  of  Ammonia. — Hydrogen  and  nitrogen  do 
not  unite  in  mixture,  nor  by  the  aid  of  heat.     A  series  of 
electrical  sparks,  as  in  the  case  of  nitrogen  and  oxygen, 
(333,)  passed  through  a  mixture  of  hydrogen  and  nitrogen, 
will  produce  a  limited  quantity  of  ammonia.     But  it  is  only 
when  these  gases  come  together  at  the  moment   of  their 
evolution  from  previous  combination,  (nascent  state,  269,) 
and  while,  so  to  speak,  they  still  have  the  impression  of  change 
upon  them,  that  they  unite  with  freedom.    Ammonia  is  there- 
fore a  constant  product  in  the  decomposition  of  those  organic 
substances  which  contain  nitrogen.     It  is  in  fact  from  the 
destructive  distillation  of  horns,  hoofs,  and  other  highly  ni- 
trogenized  forms  of  animal  matter,  that  the  ammonia  of 
commerce  is  in  great  measure  derived. 

This  nascent  union  also  occurs  without  the  aid  of  the 
products  of  life.  A  fragment  of  metallic  iron  in  moist  air 
soon  contracts  a  film  of  oxyd  of  iron,  which,  like  other  porous 
bodies,  absorbs  the  atmospheric  gases,  while  the  electrical 
influence  of  the  oxyd  of  iron  with  water  and  metallic  iron, 
forming  in  fact  a  voltaic  circuit,  effects  a  slow  decomposition 
of  water,  whose  hydrogen  unites  in  its  nascent  state  with 
atmospheric  nitrogen  to  form  ammonia.  Thus  we  reach  an 
explanation  of  the  well-known  fact,  that  oxyd  of  iron  often 
contains  a  notable  proportion  of  ammonia. 

442.  Again  :  Hydrogen  is  evolved,  as  all  know,  by  the 
action  of  dilute  sulphuric  acid  on  zinc.     Nitric  acid  effects 
the  same  end,  if  of  a  certain  concentration.     But  if  nitric 
acid  be  added  drop  by  drop  to  dilute  sulphuric  acid,  while 
hydrogen  is  being  evolved  by  its  action  on  zinc,  the  effer- 
vescence from  escaping  hydrogen  is  checked,  and,  if  the  ad- 
dition of  nitric  acid  is  cautiously  made,  a  point  is  reached 
when  the  evolution  of  hydrogen  ceases  entirely.     The  zinc 
is  still  dissolving,  but  the  hydrogen  is  immediately  seized 
as  fast  as  it  is  evolved,  by  the  nitrogen  from  the  decomposed 
nitric  acid,  ammonia  is  formed,  and  the  fluid  is  found  to  con- 
tain a  notable  quantity  of  nitrate  and  sulphate  of  ammonia. 


441.  What  is  the  origin  of  ammonia?  How  do  the  two  gases  unite? 
How  does  this  happen  from  the  dung  of  animal  matters  ?  How  without 
their  aid?  442.  How  is  ammonia  formed  by  the  solution  of  zinc? 
Describe  the  process. 


COMPOUNDS  OF  HYDROGEN. 


263 


443.  Ammonia  was  known  to  the  ancients,  and  bears  proof 
of  its  antiquity  in  its  very  name.     They  obtained  sal-ammo- 
niac by  burning  the  dried  dung  of  camels  in  the  desert,  whence 
the  name,  ammonia,  from  ammos,  sand,  in  allusion  to  the 
desert,  which  was  also  called  Ammon,  one  of  the  names  of 
Jupiter.     The  sal-ammoniac,  sulphate  of  ammonia,  and  am- 
monia-alum, are  found   among   the  products  of  volcanos. 
Free  ammonia  is  exhaled  from  the  foliage  and  found  in  the 
juices  of  certain  plants,  in  the  perspiration  of  animals,  in 
iron  rust,  and  absorbent  earths.    Rain  water  also  contains  a 
small  quantity  of  ammoniacal  salts,  washed  out  of  the  atmo- 
sphere j  and  the  guano  so  much  valued  as  a  manure,  is  rich 
in  various  ammoniacal  compounds. 

444.  Preparation. — Ammonia  is  prepared  by  decompos- 
ing sal-ammoniac,  by  dry  lime  and  heat.     For  this  purpose 
equal  parts  of  dry  powdered  sal-ammoniac  and  freshly  slaked 
dry  lime  are  well  mingled  and  heated  in  a  glass,  or,  if  the 
quantity  is  considerable,  in  an  iron  vessel.     The  lime  takes 
the  chlorohydric  acid,  forming  chlorid  of  calcium,  and  am- 
monia is  given  out  as  a  gas.     Fig.  320  shows  the  arrange- 
ment for  the  purpose. 

The  ammonia  is  col- 
lected over  mercury. 
In  the  laboratory  it  is 
more  convenient  to 
employ  in  the  flask  e 
strong  solution  of  am- 
monia, which  yields 
a  large  volume  of  gas 
at  a  gentle  heat.  If 
it  is  required  to  dry 
the  gas,  it  cannot  be 
done  by  chlorid  of 
calcium,  which  ab- 
sorbs it  largely  in  the 


Fig.  320. 


cold,  but  dry  caustic  lime  or  potassa  must  be  used. 

445.  Properties. — The  dry  gas  is  colorless,  having  the 
very  pungent  smell  so  well  known  as  that  of  "hartshorn," 
(because  it  was  procured  formerly  from  the  horns  of  the  hart.) 


443.  What  of  the  antiquity  of  ammonia?  What  natural  sources  are 
named  for  it?  444.  How  is  it  prepared?  Describe  the  process,  tig.  320. 
445.  What  are  its  properties? 


264 


NON-METALLIC   ELEMENTS. 


It  is,  when  undiluted,  quite  irrespirable,  and  attacks  tha 
eyes,  mouth,  and  nose  powerfully.  It  is  strongly  alkaline, 
and  is  often  called  the  volatile  alkali.  It  restores  the  blue 
of  reddened  litmus,  turns  green  the  blue  of  cabbage  and 
dahlia,  and  neutralizes  the  most  powerful  acids.  Its  density 
is  about  half  that  of  air,  or  0-597.  It  does  not  support 
combustion,  but  the  flame  of  a  candle  as  it  expires  in  the 
gas  is  slightly  enlarged,  and  surrounded  with  a  yellowish 
fringe.  A  small  jet  of  ammoniacal  gas  may  also  be  burned 
in  an  atmosphere  of  oxygen.  With  its  own  volume  of  oxygen 
it  explodes  by  the  electric  spark,  and  produces  water  and 
free  nitrogen.  Passed  through  a  tube  tilled  with  iron  wire, 
and  heated  to  redness,  dry  ammonia  is  entirely  decomposed; 
yielding  for  every  200  measures  of  ammonia,  300  measures 
of  hydrogen,  and  100  of  nitrogen.  The  metal  in  the  tube 
acts  to  decompose  the  ammonia  solely  by  its  presence,  (271.) 
At  a  temperature  of  50°  it  is  liquefied  with  a  pressure  of 
6£  atmospheres,  and  with  the  ordinary  pressure  it  is  liquid 
at  — 40°,  producing  a  white,  translucent,  crystalline  solid, 
heavier  than  the  liquid. 

446.  Ammonia  is  instantly  absorbed  by  water.  A  frag- 
ment of  ice  slipped  under  the  lip  of  an  air-jar  filled  with  dry 
ammonia  over  the  mercury  cistern  is  melted  at  once,  and 
the  mercury  rapidly  rises  to  supply  the  place  of  the  absorbed 
gas.  This  forms  a  weak  solution  of  ammonia,  as  may  be 
shown  by  its  action  with  reddened  litmus.  Cold  water 
dissolves  500  times  its  volume  of  ammonia,  all  of  which  is 


How  does  it  act  with  other  bodies?  How  is  it  classed?  What  its 
density?  How  as  respects  combustion?  How  is  it  decomposed?  What 
is  the  product?  446.  How  absorbablc  is  it? 


COMPOUNDS  OF  HYDROGEN. 


265 


expelled  by  heat.  .  This  solution  is  called  aqua  ammonia?,. 
It  is  prepared  in  a  "Woulf ' s  apparatus  b,  c,  d,  (fig.  321,)  and 
is  evolved  from  dry  lime  and  sal-ammoniac  in  a.  The  tubes 
i  dip  to  the  bottom  of  the  water  in  each  bottle,  and  slight 
pressure  may  be  made  by  causing  the  last  i  to  dip  into  mer- 
cury. The  fluid  is  seen  to  mount  in  o,  o}  o,  indicating  tho 
pressure,  which  of  course  is  greatest  in  b. 

447.  Solution  of  ammonia,  if  saturated  in  the  cold,  is 
lighter  than  water,  being  sp.  gr.  0-870,  containing  32  J 
parts  in  100  of  real  ammonia.     Its  odor  is  overpowering, 
causing  suffusion  of  the  eyes  and  a  strong  alkaline  taste. 
It  boils  at  130°,  and  freezes  only  at  — 40°.     It  saturates 
acids,  and  forms  definite  salts.     Ammonia  is  always  recog- 
nized by  its  odor  and  its  restoring  the  blue  of  reddened 
litmus,  carrying  other  vegetable  blues  to  green,  and  browning 
yellow  turmeric.     Its  salts  are  decomposed  by  dry  lime  or 
caustic  potassa,  evolving  the  characteristic  ammomacal  odor. 
A  rod  moistened  in  chlorohydric  acid  brought 

near  a  vessel  evolving  ammonia  causes  an  imme- 
diate cloud  of  chlorid  of  ammonium,  (fig.  322.) 
It  must  be  preserved  in  well-stopped  bottles  in 
a  cool  place,  as  the  heat  of  summer  or  of  a  warm 
room  causes  gas  enough  to  be  evolved  to  blow 
out  the  stopper  of  the  bottle.  Fig.  322. 

448.  Hydrogen  and  Phosphorus. — Phosphurettcd  Hydro- 
gen.— This  gaseous  body  is  conveniently  prepared  by  em- 
ploying quicklime  recently  slacked,  water,  and  a  few  sticks 
of  phosphorus,  in  a  small  retort,  (fig.  323,)  the  ball  of  which 


Fig.  323. 
is  nearly  filled  with  the  mixture.     A  gentle  heat  generates 

How  is  aqua  ammoniae  formed  ?  Describe  Wottlf ' s  apparatus.  447. 
What  are  the  properties  of  the  solution  ?  How  are  its  salts  decomposed  ? 
448.  How  is  phosphuretted  hydrogen  obtained  ? 


266  NON-METALLIC   ELEMENTS. 

the  gas,  which  breaks  from  the  surface  of 
the  water  (beneath  which  the  beak  of  the 
retort  dips  very  slightly)  in  bubbles,  that 
inflame  spontaneously  as  they  reach  the  air, 
rising  in  beautiful  wreaths  of  smoke,  which 
float  in  concentric,  expanding  rings.    Phos- 
phuret  of  calcium  thrown  into  a  glass  of 
water  (fig.  324)  is  instantly  decomposed,  and 
evolves  the  spontaneously  inflammable  gas. 
Fig.  324.         Chlorohydric  acid   evolves  from  this  com- 
pound the  variety  of  this  gas  which  is  not  spontaneously 
inflammable. 

449.  Properties. — This  gas  has  a  digusting,  heavy  odor, 
like  putrid  fish,  which  is  far  more  annoying  than  that  of 
sulphuretted  hydrogen.    It  is  transparent  and  colorless,  has  a 
bitter  taste,  and,  if  dry,  may  be  kept  unchanged  either  in  the 
light  or  dark.     It  loses  its  spontaneous  inflammability  by 
standing  a  time  over  water,  a  body  being  deposited  which 
is   probably   phosphorus,    in   its   red   modification.     It   is 
deadly  when  breathed.     It  acts  very  violently  with  oxygen 
gas.     If  bubbles  of  it  are  allowed  to  enter  ajar  of  oxygen, 
each  bubble  burns  with  a  most  brilliant  light  and  a  sharp 
explosion.     The  mixture  of  even  a  very  small  quantity  with 
oxygen  would  be  quite  hazardous,  destroying  the  vessels. 
Its  property  of  spontaneous  inflammability  is  undoubtedly 
owing  to  a  portion  of  free  vapor  of  phosphorus.     In  its 
chemical  relations  phosphuretted  hydrogen  is  nearly  neutral, 
but  is  in  some  respects  a  base,  as  it  forms  crystalline  salts 
with  bromohydric  and  iodehydric  acids,  which  are  decom- 
posed again  by  water. 

There  are  three  phosphurets  of  hydrogen,  PaH,  PH2,  and 
PH3.  The  second  of  these  is  a  liquid,  the  third  is  the  sub- 
stance described  above. 

Compounds  of  Hydrogen  with  the  Carbon  Group. 

450.  Carbon   and   Hydrogen   form  a  vast   number   of 
compounds  in  the  organic  kingdom,  many  of  which  will 
come  under  our  consideration   in  the  organic  chemistry. 


449.  What  are  its  properties?  What  is  its  most  remarkable  pro- 
perty  ?  What  its  constitution  ?  450.  What  compounds  of  hydrogen  and 
tarbon  are  named  ? 


COMPOUNDS  OF  HYDROGEN.  267 

There  are  two  gases,  marsh  gas  and  olefiant  gas,  or  the 
light  and  heavy  carburetted  hydrogens,  which  are  found  in 
the  inorganic  kingdom,  although  they  are  derived  from  the 
destruction  of  organic  bodies.  These  two  compounds  we 
will  now  consider.  They  are — 

Light  carburetted  hydrogen  gas CHa      or     CSH4 

Olefiant,  or  heavy  carburetted  hydrogen  gas...  CaIIa     "     C4H4 

451.  Liglit    Carburetted  Hydrogen    Gas;    Marsh   Gas; 
Fire  Damp. — This  gas  occurs  abundantly  in  nature,  being 
formed  nearly  pure  by  the  decomposition  of  vegetable  mat- 
ter under  water,  (marsh  gas.)    The  bubbles  which  rise  when 
the  leaves  and  mud  of  a  stagnant  pool  or  lake  are  stirred, 
are  light  carburetted  hydrogen,  with  some  nitrogen  and  car- 
bonic acid.     It  may  be  collected  in  such  situations  by  means 
of  an  inverted  funnel  and  bottle,  as 

in  figure  325.     In  coal  mines  it  is 
copiously  evolved  in  company  with 
heavy  carburetted    hydrogen    and 
carbonic  acid,  (fire  damp.)    In  the  | 
salt  region  of   Kanawha,  it  flows  =] 
so  abundantly  from  the   artesian 
wells  with  the  salt  water,  as  to  fur- 
nish heat  enough  by  its  combustion 
for  evaporating  the  salt  water.  The 
village  of  Fredonia,  in  New  York,  Fis-  325- . 

has  for  many  years  been  illuminated  with  this  gas,  derived 
from  the  saliferous  deposits. 

452.  Preparation. — Marsh  gas  is  prepared  by  treating 
equal  parts  of  acetate  of  soda  and  solid  hydrate  of  potash 
with  one  and  a  half  parts  of  quicklime.     The  materials  are 
ground  separately,  well  mingled,  and  strongly  heated  in  a 
retort  of  hard  glass  protected  by  a  thin  sand-bath  of  sheet- 
iron.     The  acetic  acid  C4H404  of  the  acetate  is  decomposed 
by  the  potash,  which  removes  from  it  2  equivalents  of  car- 
bonic acid,  and  marsh  gas  is  evolved,  thus: 

Acetic  acid C4H404  =  Carbonic  acid,  2  equivalents Ca     04 

Marsh  gas GjIU 

C4H404  C»II404 


Give  their  composition.  451.  What  is  marsh  gas  ?  How  may  it  bt» 
collected  ?  What  other  natural  sources  are  named  ?  452.  How  is  it  pre- 
pared ?  Give  the  reaction. 


'268 


NON-METALLIC   ELEMENTS. 


The  lime  preserves  the  glass  of  the  retort  from  the  action 
of  the  potash. 

453.  Properties. — Marsh    gas    is    colorless,   inodorous, 
slightly  absorbed  by  water,  and  is  respirable  when  mingled 
with  common  air.     Its  weight  is  about  half  that  of  air,  or 
•559,  and  100  cubic  inches  weigh  1741  grains.     It  burns 
with  a  yellow  flame,  giving  as  the  products  of  combustion 
water  and  carbonic  acid.      Mingled  with  common   air,  it 
forms  an  explosive  mixture,  which  collects  in  large  quantities 
in  the  upper  part  of  the  galleries  of  coal-mines,  giving  origin 
to  fearful  explosions  and  the  destruction  of  many  lives  of 
miners.     Twice  its  volume  of  oxygen  burns  it  completely. 
It  has  never  been  liquefied.     In  a  tube  of  porcelain,  at  full 
redness,  it  is  decomposed,  carbon  is  deposited,  and  hydrogen 
evolved.     With  moist  chlorine  in  the    sunlight,  it  forms 
carbonic  and  chlorohydric  acids,  but  is  not  affected  by  it  in 
the  dark.     It  is  composed  in  100  parts,  of  hydrogen  25, 
vapor  of  carbon  75 ;  or  by  volume,  of 

2  volumes  of  hydrogen =  0-696X2=  0-1392 

and  i  volume  of  carbon  vapor =    -829 -r- 2  =  0-4145 

Theoretical  density  of  marsh  gas 0-5537 

454.  Olrfiant  Gas,  or  heavy  Citrluretted  Hydrogen  Gas. 
— This  gas  was  discovered  in  1796,  bv  an  association  of 
Dutch  chemists,  who  gave  it  the  name  of  olefiant,  because  it 
forms  a  peculiar  oil-like  body  with  chlorine.     It  is  prepared 
by  mixing  strong  alcohol  with  five  or  six  times  its  weight 
of  oil  of  vitriol  in  a  capacious  retort,  and  applying  heat  to 
the  mixture.    The  action  is  complicated,  and  cannot  be  well 
explained  at  this  time.     The  gaseous  products  are  olefiant 
gas,  carbonic  acid,  and  sulphurous  acid.     The  alcohol  is 


453.  What  are  its  properties?     What  danger  arises  from  it  in  coal- 
mines ?    How  is  it  composed  by  volume  ?     454.  How  is  it  prepared  ? 


COMPOUNDS  OF  HYDROGEN.  269 

charred,  and  at  the  end  of  the  operation  froths  up  very  much. 
The  gas  can  be  purified  by  passing  it  first  through  a  wash- 
bottle  containing  a  solution  of  potash,  and  then  through  oil 
of  vitriol ;  the  potash  removes  the  acid  vapors,  and  the  oil 
of  vitriol  retains  the  ether,  (fig.  326.) 

455.  Properties. — Olefiant   gas   is   a   neutral,   colorless, 
tasteless  gas,   nearly  inodorous,  and   having  a  density  of 
0-9784;  100  cubic  inches  of  it  weighing  30  57  grains.     It 
burns  with  a  most  brilliant  white  light  and  evolves  much 
free  carbon.     With  three  volumes  of  oxygen  gas  it  burns 
completely,   with   a  tremendous  detonation,   which  is  too 
severe  even  for  very  strong  glass  vessels.    Bubbles  of  the  mix- 
ture may  be  exploded  by  a  burning  paper,  as  they  rise  from 
beneath  the  surface  of  water.    Water  and  carbonic  acid  are 
the  sole  products  of  this  combustion.     It  is  partially  decom- 
posed by  passing  through  tubes  heated  to  redness,  and  much 
carbon  is  deposited.    This  effect  happens  in  the  iron  retorts 
of  city  gas-works,  in  which  crusts  of  pure  carbon,  sometimes 
of  great  thickness,  accumulate  from  the  decomposition  of 
the  gas.     100  parts  of  olefiant  gas  contain  200  hydrogen 
and  100  vapor  of  carbon.     Thus, 

2  volumes  of  hydrogen  weigh 0-1392  14-29 

1  volume  of  carbon  vapor 0-8290  85-71 

0-9672  100-00 

Its  formula  is  thence  C4H4,  and  the  experimental  density 
(0-9784)  is  a  near  approach  to  the  theoretical. 

456.  The  chlorine  compound  will   be  described   in  the 
organic  kingdom.     It  burns  with  chlorine,  forming  chloro- 
hydric  acid,  and  depositing  its  carbon   in  a  dense   cloud. 
Illuminating  gas  is  formed  of  a  union  of  marsh  gas  and  of 
olefiant  with  some  free  hydrogen.     The  power  of  illumination 
is  derived  from  the  olefiant  gas.     Ammonia,  its  sulphuret, 
carbonic  acid,  tar,  and  resinous  pyrogenic  compounds  require 
to  be  removed  from  coal  gas  before  it  is  fit  for  use ;  and  this 
is  accomplished  by  passing  it  through  water,  cooling  it  in  con- 
densers, and  transmitting  it  through  dry  lime  purifiers,  and 
through  dilute  solution  of  sulphate  of  iron  to  remove  HS 
and  C03. 

The  other  compounds  of  hydrogen  with  boron,  &c.,  are 
too  little  known  to  require  description  now. 

455.  What  its  properties  ?  How  much  oxygen  burns  it  ?  What  are 
the  products  ?  How  decomposed  ?  What  is  its  composition  ?  456.  Whenco 
its  name  ?  What  is  illuminating  gas  ? 


270  COMBUSTION. 


Combustion ,  and  the  Structure  of  Flame. 

457.  Combustion. — This  familiar  phenomenon  is  the  dis- 
engagement  of  light  and  heat  which  accompanies  some  cases 
of  chemical  union.     Nearly  all  our  operations  being  per- 
formed in  the  atmosphere,  the  term  combustion  has  come  to 
be  restricted,  in  a  popular  sense,  to  the  union  of  bodies  with 
oxygen,  with  development  of  light  and  heat.     Thus,  carbon, 
sulphur,  phosphorus,  &c.,  are  familiar  examples  of  elementary 
combustibles,  while  oil,  tar,  coal,  wood,  &c.,  are  compound 
ones.     The  products  of  the  combustion  of  organic  bodies 
are  all   gases  or  vapors,  and  are  no  longer  combustible; 
while  the  products  of  the  combustion  of  iron,  phosphorus, 
potassium  &c.,  are  oxyds,  bases,  or  acids,  and  generally  are 
incapable  of  further  change  from  similar  action.     Thus,  iron 
burns  brilliantly  in  oxygen    gas,  (277,)  forming   a  com- 
pound, capable  of  no  further  change  in  oxygen.     Iron  also 
burns  in  vapor  of  sulphur,  (fig.  232,)  but  the  protosulphuret 
of  iron  so  formed  is  still  capable   of  burning  in  oxygen. 
For  such  reasons  as  these,  bodies  were  for  a  long  time  di- 
vided by  chemists  into   two  classes,  of  combustibles   and 
supporters  of  combustion.     This  mode  of  arrangement   is 
now  for  the  most  part  abandoned.     It  was  radically  defective 
as  a  philosophical  classification  of  elements,  since  it  seized 
on  a  single  phenomenon  accompanying  chemical  union,  and 
disregarded  all  those  natural  analogies  which  group  the  ele- 
ments into  distinct  classes. 

458.  In  all  cases  of  combustion  the  action  is  reciprocal. 
Hydrogen  burns  in  common  air ;  but  if  a  stream  of  oxygen 
is  thrown  into  a  jar  of  hydrogen,  through  a  small  aperture 
at  the  top,  when  the  latter  is  burning,  the  flame  is  carried 
down  into  the  body  of  the  jar,  and  the  oxygen  will  continue 
to  burn  in  the  hydrogen,  as  it  issues  from  the  jet.     In  this 
case  the  oxygen  may  be  said  to  be  the  combustible,  and  the 
hydrogen  the  supporter.     The   simple   statement  in   both 
cases  is,  that  oxygen  and  hydrogen  combine,  and  combus- 
tion— that  is,  the  disengagement  of  light  and  heat — is  the 
consequence.  (Daniell.)     The  diamond  burns  in  oxygen  gas, 
but  the  latter  is  as  much  altered  by  the  union  as  the  former ; 

457.  What  is  combustion  ?  How  is  the  term  restricted  ?  What  division 
of  elements  was  founded  on  this  phenomenon?  458.  What  of  ^he  re- 
ciprocal nature  of  combustion  ?  What  of  light  and  heat  evolved  ? 


COMBUSTION.  271 

and  wo  cannot  therefore  say  whether  the  oxygen  or  the 
carbon  is  the  most  burnt.  Heat  and  light  attend  this  union  : 
but  the  carbon  of  the  human  body  is  as  truly  burnt  in  the 
lungs  by  the  atmospheric  oxygen,  as  is  the  fuel  on  our  fires. 
The  product  of  this  combustion,  the  carbonic  acid,  thrown 
out  by  the  lungs  at  every  exhalation,  is  the  same  thing  as 
the  carbonic  acid  which  is  discharged  at  the  mouth  of  a 
furnace.  In  the  case  of  the  animal  body,  the  combustion  is 
so  slow  that  no  light  is  evolved,  and  only  that  degree  of  heat 
(98°  to  100°)  which  is  essential  to  vitality.  The  term 
combustion  must  have,  then,  a  chemical  sense  vastly  more 
comprehensive  than  its  popular  meaning.  The  rust  which 
slowly  corrodes  and  destroys  our  strongest  fixtures  of  iron, 
and  the  gradual  process  of  decay  which  reduces  all  structures 
of  wood  to  a  black  mould,  are  to  the  chemist  as  truly  cases 
of  combustion  as  those  more  rapid  combinations  with  oxy- 
gen which  are  accompanied  by  the  splendid  evolution  of 
light  and  heat. 

The  heat  produced  by  combustion  has  received  no  satis- 
factory explanation.  We  know  that  any  change  of  state  in 
a  body  is  accompanied  by  an  alteration  of  temperature. 
When  two  liquids  become  solid,  we  can  better  understand 
why  heat  should  be  produced,  (124.)  But  why  the  union 
of  carbon  and  oxygen,  or  of  oxygen  with  hydrogen,  to 
form  a  gas,  should  evolve  such  intense  heat  as  to  fuse  the 
most  refractory  bodies,  is  as  yet  unexplained. 

459.  Bodies  become  visible  in  the  dark  at  about  1000° 
of  heat.  This  fact  has  been  lately  confirmed  by  the  re- 
searches of  Draper,  on  the  shining  by  heat  of  a  strip  of 
platinum  in  the  dark,  when  heated  by  a  current  of  voltaic 
electricity.  It  is  true  of  all  bodies  capable  of  being  heated, 
whether  solids,  or  fluids,  as  melted  metals.  It  is  impossible 
by  any  means  to  render  a  gaseous  body  visibly  red.  A 
coil  of  platinum  wire  suspended  in  the  current  of  air  escap- 
ing from  an  argand-lamp  chimney  is  at  once  heated  to  red- 
ness,  while,  as  every  one  knows,  the  hot  air  itself  is  entirely 
invisible.  Combustible  gases  heated  to  a  certain  point  in 
the  air,  take  fire  and  burn,  as  when  we  apply  to  our  gas- 
burner  the  flame  of  a  match.  The  color  of  red-hot  bodies  de- 
pends on  the  temperature.  Yellow  light  begins  to  be  evolved 

What  chemical  extension  is  given  to  the  term  ?  Whence  the  heat 
evolved  in  combustion  ?  459.  At  what  temperature  do  bodies  become 
visible  in  the  dark? 


272  NON-METALLIC    ELEMENTS. 

at  about  1325°,  and  at  2130°  all  the  colors  of  the  spec 
trum  were-  observed  by  Draper  in  the  light  viewed  by  a 
prism  as  it  came  from  incandescent  platinum.  A  full  white 
heat,  seen  by  day-light,  is  supposed  to  be  at  least  3000°. 
The  increase  of  brilliancy  in  the  light  from  hot  bodies  is  at 
a  much  higher  ratio  than  the  temperature.  Thus,  the  same 
observer  found  the  "brilliancy  of  light  at  2590°  more  than 
thirty-six  times  as  great  as  it  was  at  1900°. 

Of  Flame. 

460.  The  structure  and  nature  of  flame  deserve  particu- 
lar notice.  If  we  look  attentively  at  the  flame  of  a 
candle,  (fig.  327,)  we  see  that  it  is  formed  of  several 
distinct  parts,  wrapped,  so  to  speak,  conically  about 
each  other.  1st.  There  is  the  interior  cone  a  a',  form- 
ed entirely  of  combustible  gases,  and  giving  no  light. 
2d.  The  cone  efg,  which  is  very  brilliant,  and  where 
the  gaseous  contents  of  the  first  portion  become 
mingled  with  atmospheric  oxygen  ;  the  hydrogen  is 
burned,  and  the  carbon,  precipitated  in  minute  parti- 
cles, reflects  light  powerfully.  And  3d.  We  see  the 
thin  outer  envelope  c  d  b,  where  the  combustion  is 
completed,  but  where  there  is  much  less  brilliancy  of 
illumination  than  incfy.  In  the  flame  of  a  gas  jet  A, 
Fig.  327.  (fig.  328,)  the  same  parts  are  recognized,  similarly  let- 

i<r  tered,  simplified  by  the  absence  of  the  candle-wick, 
whose  place  is  occupied  by  the  ascending  stream  of  gas. 
A  section  of  the  candle-flame  midway  between  a  a' 
would  give  us  three  distinct  rings,  each  marked  by  its 
own  chemical  condition.  In  the  centre  is  the  olefiant 
gas  of  the  decomposed  fat  H,  (fig.  329.)  The  hydro- 
gen of  this  burns  first,  forming  water,  and  the  carbon  is 
raised  by  the  heat  of  the  burning  hydrogen  to  white- 
ness,  and  fills  the  space  c;  while,  exte- 
rior it,  the  thin  film  o  is  formed  from 
the  union  of  the  carbon  with  oxygen  to 
form  carbonic  acid.  Flame  may  therefore 
be  considered  as  a  hollow  cone  of  ignited 
jsig.  328.  combustible  gas,  covering  as  with  a  shell  FlS-  329> 

What  was  Draper's  experiment?  What,  is  the  temperature  of  yellow 
light?  What  the  brilliancy  as  compared  with  temperature?  What  is 
noticed  in  the  structure  of  flame?  Describe  fig.  327.  What  are  the 
parts  of  th )  flame  ?  Define  flame. 


FLAME. 


273 


Fig.  330. 


an  interior  unignited  mass  of  inflammable  gas.  This  is  easily 
demonstrated  by  introducing  a  small  tube  of  glass  Z>,  fig.  330, 
into  the  cone  H,  by  which  a  portion  of  the  inflammable 
gas  is  led  out  and  may  be  burnt  at  the 
open  end  of  the  tube.  In  like  man- 
ner, by  bringing  a  sheet  of  platinum 
foil  over  the  flame  of  a  large  spirit- 
lamp,  it  will  be  heated  to  redness  in  a 
ring  on  the  outer  circle,  while  the 
centre  remains  black,  showing  that  the 
interior  is  comparatively  cold.  Phos- 
phorus fully  ignited  in  a  metallic 
spoon,  is  at  once  extinguished  by  im- 
mersion in  the  interior  of  a  volumin- 
ous flame,  like  that  from  alcohol,  burn- 
ing in  a  small  capsule.  The  air  is  shut 
out  by  the  screen  of  flame  :  the  phosphorus,  finding  no  oxy- 
gen, goes  out,  but  may  be  seen  fused  in  the  spoon :  bringing 
it  again  to  the  air,  it  is  rekindled,  and  so  on. 

461.  A  high  temperature,  it  will  be  easily  seen,  is  an 
indispensable  condition  for  a  perfect  and  brilliant  combus- 
tion, as  the  light  reflected  from  the  ignited  carbon  is  vastly 
greater  at  3000°  than  at  2500°,  (459.)  A  plentiful  supply 
of  oxygen  is  of  course  the  antecedent  of  a  perfect  combus- 
tion. The  candle  or  lamp  becomes  smoky  whenever  these 
conditions  are  imperfectly  fulfilled — as  when  the 
wick  of  a  candle  becomes  too  long  and  reduces  the 
temperature  of  the  flame  below  the  point  of  bril- 
liant combustion,  supplying  at  the  same  time  a 
superabundance  of  material.  The  candle  must 
then  be  snuffed;  or  it  may  be  provided  with  a 
fiat  plaited  wick,  as  in  fig.  331,  which  bends  out- 
ward as  it  burns,  and  coming  in  contact  with  the 
air,  consumes  as  fast  as  it  protrudes.  In  all  flames 
like  that  of  the  candle,  when  the  air  has  contact 
only  on  one  side,  combustion  is  very  imperfect.  A 
more  rapid  and  abundant  supply  of  oxygen  is  the 
object  in  the  construction  of  the  argand  and  solar 
lamps  and  all  similar  contrivances.  Fig.  331. 

462.  This  is   accomplished   in    the    argand    burner   by 

How  is  it  demonstrated  by  fig.  330  ?  What  other  experiments  are  given  ? 
461.  What  are  the  conditions  of  perfect  combustion?      Why  is  a  candle 
an  imperi'ect illumination  ?   What  is  the  principle  of  the  argand  burners  ? 
18 


274 


NON-METALLIC   ELEMENTS. 


Fig.  332. 


employing  a  circular  wick  a  I  c  d  (fig. 
332)  arranged  between  the  metallic  tubea 
through  the  centre  of  which  g  h  a  draft  of 
air  rises,  as  shown  by  the  central  arrows. 
The  draft  is  made  more  powerful  by 
using  a  glass  chimney,  contracted  at  D  0 
so  as  to  deflect  the  ascending  outer  cur- 
rent of  air  strongly  against  the  flame. 
Thus,  at  the  same  instant,  fresh  supplies 
cof  oxygen  are  brought  in  contact  with 
the  inner  and  outer  surfaces  of  flame, 
which  still  retains  the  same  relation  of 
parts  as  before.  The  heat  of  combus- 
tion is  enormously  increased  by  these 
means;  and  with  the  same  amount  of 
fuel,  a  much  more  brilliant  light  is  pro- 
duced. In  the  common  double-current 
spirit-lamp,  employed  in  the  laboratory  for  high  heats,  the 
construction  is  similar,  a  metallic 
chimney  replacing  the  glass.  A  section 
of  this  lamp  is  seen  in  fig.  333.  Dr. 
C.  T.  Jackson  has  described  a  modi- 
fication of  the  double-current  spirit- 
lamp,  in  which  a  blast  of  air  from  a 
bellows  is  introduced  within  the  inner 
tube.  The  arrangement  is  such  chat 
the  blast  issues  in 
a  narrow  ring,  con- 
centric with  the  wick 
and  in  close  contact 

with  it.  Properly  manage^,  this  lamp 
forms  the  most  powerful  lamp-furnace  in 
use.  The  invention  in  fact  ap- 
plies the  principle  of  the  mouth 
blowpipe  to  the  argand  lamp. 

In  places  where  gas  is  used,, 
the   gas-lamp,    (fig.    334,)  fed1 
Fig.  334.        by  a  flexible  pipe  and  supplied 
•with  a  metallic  or  mica  chimney,  leaves  nothing 
to   be  desired  for  a  powerful  and  economical 


Describe   fig.   332.    Why  is  the  heat  increased? 
lamp  ?    What  the  gas-lamps  ? 


What  is  Jackson-, 


FLAME. 


275 


heat.  A  small  glass  spirit-lamp,  with  a  close  cover,  (fig. 
335,)  to  prevent  evaporation,  is  an  indispensable  convenience 
in  even  the  humblest  laboratory. 

463.  The  Mouth  Blowpipe  (fig.  336)  converts  the  flame  of 
a  common  lamp  or  candle  into  a  powerful  furnace.  By  the 
blast  from  the  jet  of  the  blowpipe,  the  operator  turns  the 


Fig.  336. 

flame  in  a  horizontal  direction  upon  the  object  of  experi- 
ment, at  the  same  time  that  he  supplies  to  the  interior  cone  of 
combustible  matter  a  further  quantity  of  oxygen.  The  flame 
suffers  a  remarkable  change  of  appearance  as  soon  as  the  blast 
strikes  it,  and  the  inner  blue  point  b  has  very  different  chemi- 
cal effects  from  the  exterior  or  yellow  point  c,  (fig.  337.) 
Immediately  before  the 
exterior  flame  is  a  stream 
of  intensely  heated  air, 
which  is  capable  of  pow- 
erfully oxydizing  a  body 
held  in  it,  and  this  point 
is  therefore  called  the 
oxydizing  flame.  The 
inner  or  blue  point  6  a  is  called  the  reducing  flame,  and  in 
it  all  metallic  oxyds  capable  of  reduction  are  easily  brought 
to  the  metallic  state  or  to  a  lower  degree  of  oxydation.  Be- 
tween the  outer  and  inner  flames  is  a  point  of  most  intense 
heat,  where  refractory  bodies  are  easily  melted.  Charcoal 
is  generally  employed  to  support  bodies  before  the  blow- 
pipe flame,  when  we  would  heat  them  in  contact  with  car- 
bon. Forceps  of  platinum  are  used  to  hold  the  substance 
when  it  is  to  be  heated  alone. 

If  the  substance  is  to  be  submitted  to  the  action  of  borax, 


463.  What  is  the  principle  of  the  mouth  blow  pipe  ?  What  parts 
are  noted  in  the  flame  before  the  jet,fig.  337  ?  What  is  the  reducing  and 
what  the  oxydizing  flame  ? 


276  NON-METALLIC    ELEMENTS. 

or  of  carbonate  of  soda, 
or  any  similar  reagent,  a 
small  platinum  wire,  bent 
into  a  loop  at  one  end, 
is  used  to  hold  the  fused 
globule,  as  seen  in  fig. 
338.  Then,  by  varying 
Fig.  338.  its  position  in  the  flame 

as  above  described,  we  may  submit  it  successively  to  the 
reducing  agency  of  carbon  vapor,  and  oxyd  of  carbon  at  J, 
to  the  intense  heat  of  burning  carbon  at  c,  or  to  the  power- 
ful oxydizing  influence  of  the  current  of  hot  air  immediately 
in  front  of  the  point  c.  The  art  of  blowing  an  unintermit- 
ting  stream  is  soon  acquired,  by  breathing  at  the  same  time 
through  the  mouth  and  nostrils ;  and  an  experienced  opera- 
tor will  blow  a  long  time  without  fatigue.  No  instrument 
is  more  useful  to  the  chemist  and  mineralogist  than  the 
mouth  blowpipe.  By  its  means  we  may  in  a  few  moments 
submit  a  body  to  all  the  changes  of  heat,  or  the  action  of 
reagents,  which  can  be  accomplished  with  a  powerful  furnace. 

Sufcty  Lamp. 

464.  The  temperature  of  flame  may  be  so  reduced  by 
bringing  cold  metallic  bodies  near  it  as  to  be  extin- 
guished. Davy  also  observed  that  a  mixture  of  explosive 
gases,  could  not  be  fired  through  a  long  narrow  orifice  like 
a  small  tube.  On  these  simple  facts  rests  the  power  of  the 
"  safety  lamp"  of  Sir  Humphry  Davy  to  protect  the  life  of 
the  miner.  If  a  narrow  coil  of  copper  wire,  (fig.  339,)  be 
^  brought  over  a  candle  or  lamp  so  as  to 

encircle  it,  the  flame  will  be  extin- 
Fig.  339.  guished;  but  if  the  wire  be  previously 

heated  to  redness,  the  flame  continues  to  burn.  The  same 
effect  will  be  produced  by  a  small  metallic  tube.  A  wire  held 
in  the  flame  is  seen  to  be  surrounded  with  a  ring  of  non-lu- 
minous matter.  If  many  wires,  in  the  form  of  a  gauze,  are 
brought  near  the  flame  of  a  candle,  it  will  be  cut  off  and 
extinguished  above  ;  only  a  current  of  heated  air  and  smoko 
will  be  seen  ascending,  (fig.  340,)  while  the  flame  continues 
to  burn  beneath,  and  heats  the  wire  gauze  red-hot  in  a  ring, 
marking  the  limits  of  the  flame.  The  flame  may  be  relighted 

464.  What  is  the  effect  of  a  cold  body  on  flame  ?  What  was  Davy'a 
observation  ? 


FLAME. 


277 


above  the  gauze,  and  will  then  burn  as  usual,  as  seen  in 

fig.  341.     Sir   Humphry  Davy  found  that  a  wire  gauze 

would  in  all  cases  arrest 

the   progress   of    flame, 

and  that  a   mixture   of 

explosive  gases  could  not 

be  fired  through  it.     A 

wire  gauze  is  only  a  series 

of    very    short     square 

tubes,  and  their   power 

to    arrest    flame    comes          Fig.  340.  Fig.  341. 

from  the  fact  that  they  cool  the  gases  below  their  point  of 

ignition.     Happily,  the  heat  required  to  ignite  the  carbon 

gases  is  much  higher  than  that  which  causes  the  union  of 

oxygen  and  hydrogen. 

465.  The  fire  damp  or  explosive  atmosphere  of  coal- 
mines, is  a  mixture  of  light  and  heavy  carburetted  hydro- 
gen, with  many  times  their  volume  of  common  air.  These 
gases,  being  lighter  than  the  air,  are  found  especially  in  the 
upper  part  of  the  galleries  of  mines,  and  when  the  naked 
flame  of  the  miner's  lamp  meets  such  an  atmosphere,  a  terrible 
explosion  often  follows.  These  explosions  in  coal-mines  b«.vo 
destroyed  thousands  of  those  whose  duties  requir- 
ed them  to  submit  to  the  exposure.  To  avoid  these 
lamentable  accidents,  Davy  invented  the  safety 
lamp.  This  is  only  a  common  lamp  surrounded 
by  a  cage  of  wire  gauze,  completely  enclosing  the 
flame,  (fig.  342.)  When  this  lamp  is  placed  in  an 
explosive  atmosphere,  the  gas  enters  the  cage, 
enlarges  the  flame  on  the  wick,  and  burns  quietly, 
the  gauze  effectually  preventing  the  passage  of 
the  flame  outward.  We  thus  enter  the  camp  of 
the  enemy,  disarm  him,  and  make  him  labor  for 
us.  The  miner  is  not  only  protected  by  this  in- 
strument, but  ig  rendered  conscious  of  the  danger 
by  the  enlargement  of  the  flame.  As  long  as  the 
lamp  can  burn,  it  is  safe  to  stay,  as  an  irrespira- 
ble  atmosphere  would  extinguish  the  flame.  The 
powerful  blast  of  wind  which  sometimes  sweeps  Fig.  3*2. 

Explain  figs.  340  and  841.  What  is  the  application  ?  What  peculiari- 
ty is  noticed  of  the  carbohydrogen  gases?  465.  What  is  the  fire  damp  ? 
Where  does  it  chiefly  collect?  How  was  Davy's  lamp  constructed? 
What  is  its  action? 


278  METALLIC    ELEMENTS. 

through  the  mines  may  render  the  lamp  unsafe,  by  forcing 
the  flame  against  the  gauze,  until  it  is  heated  so  hot  as  to 
inflame  the  external  atmosphere.  This  accident  is  prevented 
by  the  addition  of  a  glass  to  cover  the  sides,  the  air  being 
admitted  from  below  through  flat  gauze  discs. 

II.  METALLIC  ELEMENTS. 
General  Properties  of  Metals. 

466.  The  number  of  the  metals  is  forty-eight,  of  which 
about  half  are  entirely  unknown,  except  in  the  laboratory, 
and  as  the  rarest  minerals  in  our  cabinets.     Of  the  other 
half,  only  fourteen  or  fifteen  are  familiarly  known,  or  pos- 
sess in  a  remarkable  degree  those  qualities  of  ductility,  lustre, 
and  malleability,  which  are  inseparable  from  our  common 
notions  of  the  metallic  character. 

A  metal  is  an  opaque  body,  of  a  peculiar  brilliancy,  de- 
scribed as  the  metallic  lustre.  It  conducts  heat  and  elec- 
tricity, and  in  electrolysis  it  goes  to  the  negative  pole  of  the 
voltaic  battery,  and  is  therefore  an  electro-positive  body. 
These  are  the  chief  characters  peculiar  to  the  class. 

Metallic  Veins. 

467.  In  nature,  the  metals  exist  commonly  in  union  with 
sulphur,  oxygen,  and  arsenic.     A  few,  as  gold,  copper,  pla- 
tinum, and  mercury,  are  found  native,  or  uncombined,  or 
are  occasionally  alloyed  with  each  other,  as  native  gold  nearly 
always  contains  a  portion  of  silver.     When  the  metals  are 
combined  with  sulphur,  or  other  mineralizing  agents,  by 
which  their  proper  metallic  characters  are  masked  or  con- 
cealed, they  are  called  ores.     The  native  metals,  gold,  cop- 
per, platinum,  &c.,  are  not  properly  denominated  ores,  being 
obtained  in  a  metallic  state  from  the  sands.     The  discovery 
and  extraction  of  the  ores  of  the  metals  constitutes  the  art 
of  milting.     The  separation  of  the  metals  from  their  ores,  by 
heat  or  other  means,  is  a  separate  branch  of  chemical  art, 
known  as  metallurgy.    Mining  demands  a  minute  knowledge 
of  the. mineralogical  character  of  the  ores  of  metals  and  of 

466.  What  is  the  number  of  metals  ?  How  many  are  commonly  known  ? 
What  is  a  metal?  467.  How  do  the  metals  exist  in  nature?  What  are 
ores?  What  is  mining?  What  is  metallurgy  ?  What  does  mining  re- 
quire ? 


METALLIC    VEINS. 


279 


the  earthy  minerals  with  which  these  are  associated  ;  as  well 
as  the  mode  of  occurrence  of  mineral  veins  and  ore  beds,  and 
the  mechanical  methods  adopted  for  the  raising  of  the  ores 
from  the  earth,  their  separation  from  foreign  substances,  and 
their  preparation  for  market. 

468.  The  ores  of  metals  are  seldom  scattered  through  the 
rocks  in  a  diffused  manner,  but  are  usually  collected  in  veins 
or  lodes,  accompanied  by  quartz,  carbonate  of  lime,  and 
various  other  minerals,  called  the  vein-stone,  or  gangue.  The 
metal-bearing  veins  occur  more  frequently  in  regions  where 
primitive  rocks  abound,  as  in  granite  and  its  associates. 
Often,  however,  they  extend  from  these  rocks  to  those  which 
rest  above  them,  and  are  stratified  ;  showing  that  the  veins 
fill  fissures  in  the  earth,  occasioned  by  the  cooling  of  its 
heated  mass,  and  into  which  the  minerals  now  filling  them 
came  by  injection  or  infiltration.  These  fissures  usually  occur 
together,  in  a  degree  of  order,  the  veins  being  more  or  less 
parallel,  as  seen  in 
c,c,c,&c.,(fig.343,) 
which  is  an  ideal  sec- 
tion of  a  metallic 
deposit,  (the  veins 
are  here  seen  to 
reach  from  the  gra- 
nite c  to  the  stratifi- 
ed rocks  a,  a.)  Cross 
veins,  or  courses, 
often  intersect  in  a 
different  direction, 
as  d,  e,  &c.  ,  and  these 
have  usually  a  mi- 
neral character  entirely  distinct,  and  showing  a  different  age 
and  origin.  At  the  intersection  of  veins  there  is  usually 
an  enlargement  of  the  lode,  and  often  a  more  abundant 
deposit  of  the  metallic  ore.  It  is  very  rare,  if  ever,  that  the 
metallic  ore  fills  the  vein  entirely.  It  usually  forms  small 
threads  running  through  the  vein-stone,  now  expanding,  and 
again  contracting,  as  seen  in  the  vertical  section  of  a  vein  in 
fig.  344,  where  a,  b,  c  show  the  rocky  gangue  surrounding 


468.  How  are  ores  found?  What  is  a  vein-stone  or  gangue?  Wnere 
do  veins  most  frequently  occur?  Describe  fig.  343.  Where  are  veins 
enlarged  ?  How  is  the  ore  usually  distributed  in  mineral  veins  ? 


'280 


METALLIC   ELEMENTS. 


the  metallic  ore  d,  e,  f,  g.  Often  the 
ore  dies  out  entirely,  as  at  b,  c,  and  is 
again  renewed  farther  on.  A  few 
minerals  only  are  found  in  beds  re- 
gularly stratified  between  layers  of 
other  rocks.  Some  of  the  ores  of 
iron  are  so  found,  as  well  as  coal  and 
rock-salt.  But  the  mode  of  origin 
of  these  last  is  quite  distinct  from 
that  of  the  ores  of  the  metals.  Fig. 
345  shows  the  mode  of  occurrence 


Fig.  345. 

of  rock-salt  in  masses,  filling  cavities  formed  probably  by 
the  solution  of  minerals  previously  existing  there. 

Physical  Properties  of  Metals. 

469.  The  physical  properties  of  the  metals  include  their  den- 
sit}',  lustre,  color, opacity,  malleability,ductility,  laminability, 
tenacity,  crystallization,  fusibility,  and  conducting  power. 
In  density,  metals  present  every  variety,  from  potassium 
(•865)  and  sodium,  (-972,)  floating  on  water,  to  gold  (19-26) 
and  platiua,  (21-5,)  the  heaviest  bodies  known.  In  lustre  they 
range  from  the  splendor  of  gold  and  of  burnished  silver,  to 
the  dulness  of  manganese  and  of  chromium.  This  property 
often  depends  on  the  mechanical  condition  of  the  metal ; 
thus,  gold  and  platinum,  as  thrown  down  from  solution  in  fine 
powder,  are  dull  yellowish-brown,  and  black  powders,  which 
show  the  lustre  and  color  appropriate  to  the  metals  only 
under  the  burnisher.  The  color  of  most  of  the  metals  is 
dull  white  or  gray.  Silver  is  nearly  pure  white ;  gold,  yel- 

Describe  fig.  344.  What  substances  arc  found  in  beds  ?  What  is  .sluivrr, 
in  fig.  345  ?  469.  What  are  the  physical  properties  of  metals  ?  What  of 
density?  What  of  lustre?  How  do  mechanical  conditions  affect  lustre? 


PHYSICAL   PROPERTIES    OF    METALS.  281 

low;  and  copper  and  titanium  are  red.  Copper  is  the  basis 
of  all  colored  alloys;  being  fused  with  tin  and  zinc  to  form 
bell  and  gun  metal  and  yellow  brass.  To  determine  the 
color  of  a  polished  metal  accurately,  the  light  must  be 
reflected  many  times  from  its  surface,  as  may  be  done  by 
placing  two  polished  surfaces  of  the  same  metal  opposite 
each  other,  and  examining  with  a  prism  the  light  reflected 
at  an  angle  of  90°  from  them.  In  this  way  it  is  found  that 
the  proper  color  of  copper  is  orange-red ;  of  gold,  after  ten 
reflections,  a  beautiful  red ;  of  silver,  a  reddish-white ;  of  zinc, 
a  delicate  indigo-blue;  of  bronze,  an  intense  red;  of  steel,  a 
feeble  violet,  &c.  In  looking  into  a  deep  vase  of  polished 
metal,  or  into  a  highly  polished  bronze  cannon,  or  the  bore 
of  a  new  steel  rifle,  these  tints  of  color  by  reflection  are  seen. 
Opacity  is  not  absolute  in  metals,  as  is  proved  in  the  case  of 
gold-leaf  on  glass,  through  which  a  beautiful  violet-green 
light  is  seen.  This  light  is  found  by  optical  experiments  to 
be  truly  transmitted  light,  and  not  a  color  caused  by  the  mi- 
nute fissures  of  the  gold-leaf.  It  is  worthy  of  remark  that 
this  greenish  color  is  complementary  to  the  red,  which  is 
the  reflected  color  of  the  gold. 

470.  Malleability,  or  the  capability  of  being  beaten  by 
blows  into  thin  leaves,  is  found  in  the  highest  perfection  in 
gold,  and  in  a  good  degree  in  many  other  metals.  Some 
metals  are  perfectly  malleable  when  cold,  as  silver,  gold, 
lead,  and  tin;  others  are  malleable  when  hot,  as  iron,  plati- 
num, &c.,  and  are  not  without  this  property,  though  in  a 
much  less  degree,  even  when  cold.  Some,  like  zinc,  are  lami- 
nable  at  a  moderate  heat,  but  brittle  above  and  below 
it;  others,  like  antimony,  are  brittle  at  all  temperatures 
short  of  fusion.  Gold  leaf  has  been  beaten  so  thin  as  to 
require  250,000  leaves  to  equal  one  inch  in  thickness,  or  1,365 
such  leaves  would  about  equal  in  thickness  one  leaf  of  this 
book.  Ductility  and  laminability  are  properties  closely 
allied  to  mallea'bility.  Iron,  for  instance,  unless  heated, 
can  not  be  beaten  like  gold,  but  it  may  be  drawn  into 
fine  wire,  (ductility,)  and  plated  by  rollers  into  thin  sheets, 
(laminability). 

"What  of  color  ?  Enumerate  colored  metals  and  alloys  ?  How  are 
metallic  colors  accurately  determined?  What  are  thus  found  to  be  the 
colors  of  gold,  of  copper,  of  silver,  zinc,  and  bronze  ?  Is  opacity  absolute  ? 
Why  not?  What  is  proved  of  the  green  color  of  gold?  To  what  is  it 
complementary?  470.  What  of  malleability,  ductility  <tc.  ? 


282 


METALLIC    ELEMENTS. 


\ 


Metals  are  rolled  in  a  machine  composed  of  two  equal 
cylinders  of  iron  or  steel,  seen  in  section 
in  fig.  346.  These  move  in  the  direction 
shown  by  the  arrows.  During  this  process, 
the  metal  becomes  more  hard  and  elastic, 

/  AM^¥\       owing   to  a   rearrangement   of  its   particles. 

/  H  H  Heated  to  a  redness  and  slowly  cooled,  it  is 
again  softened,  and  is  then  said  to  be  annealed. 
Copper  is  annealed  by  plunging  the  red-hot 
metal  into  water,  while  the  same  treatment 

renders  steel  intensely  hard. 

471.    The  tenacity  of  metals  is  compared  by  using  wires 

of  the   same  size  of  different  metals,  and   ascertaining  how 

much  weight  they  will  sustain.     Iron  is  the  most  tenacious, 

and   lead  the  least.      The  tenacity  of  wires  TJ^  of  an  inch 

in  diameter  is  equal, 


Fig.  346. 


For  Iron,  to 444  pounds. 

"    Copper 300       " 

"    Platinum 275       « 

"    Silver 171       « 

"    Gold....  ...137       " 


For  Zinc,  to 100  pounds. 

"    Nickel 97       " 

«    Tin 32       " 

"    Lead 24       " 


in 


Wires    are    drawn    through     smooth    conical    holes 

a  steel  plate,  (fig.  347,)  each  succeeding  hole 
being  a  little  less  than  its  predecessor.  In 
this  way,  wires  of  extreme  fineness  may  be 
drawn  from  several  of  the  ductile  metals.  Dr. 
Wollaston  succeeded,  by  a. peculiar  method,  in 
making  a  gold  wire  so  small  that  530  feet  of  it 
weighed  only  one  grain;  it  was  only  -5^0^  of 
an  inch  in  diameter;  and  a  platinum  wire 
was  made  by  the  same  philosopher,  of  not  more 
of  an  inch.  Metals  passed  repeatedly  through 
a  wire°plate,  also  become  stiff  and  brittle,  as  in  the  rolling 
mill. 

472.  Many  metals  crystallize  beautifully,  from  fusion,  when 
slowly  cooled,  as  described  for  sulphur,  (306 ;)  bismuth  offers 
the  most  remarkable  example  of  this  :  others  solidify  without 
crystallization,  or  the  traces  of  crystalline  structure  are  seen 
only  feebly  marked  by  lines  on  the  surface.  Copper,  gold, 


\J 
Fig.  347. 


than 


IIow  are  metals  rolled?  What  is  annealing  ?  471.  How  is  tenacity 
shown?  Give  examples.  IIow  is  air  formed ?  472.  What  of  crystal- 
lization ? 


CHEMICAL   RELATIONS    OF    METALS.  283 

silver,  platina,  and  some  other  metals  are  found  crystallized 
m  nature.  We  can  also  imitate  nature  in  this  respect  by  the 
voltaic  battery,  which  enables  us  to  procure  many  metals  in 
perfect  crystals.  Iron,  brass,  and  other  metals  often  take  on 
a  crystalline  structure  by  vibration  materially  influencing 
their  tenacity.  The  fusion  points  of  several  metals  were 
given  in  §  121. 

Many  metals  are  volatile,  of  which  mercury,  arsenic, 
tellurium,  cadmium,  zinc,  potassium,  and  sodium  are  exam- 
ples, being  volatile  below  a  red-heat.  Even  gold,  silver, 
and  platinum  are  raised  in  vapor  by  the  heat  of  the  voltaic 
focus,  (198.) 

Some  metals  assume  a  semi-fluid  or  pasty  condition  before 
melting,  such  as  platinum  and  iron,  both  of  which  can  be 
welded  or  made  to  unite  without  solder,  when  in  this  soft 
state  ;  lead,  potassium,  and  sodium  can  be  welded  in  the  cold, 
as  also  can  mercury,  when  it  is  frozen.  The  conduct- 
ing power  of  some  of  the  principal  metals  was  given  in  §  88, 
and  their  capacity  for  heat  in  §  120. 

473.  The  metals  unite  with  each  other  to  form  alloys, 
many  of  which  are  familiarly  known,  as  f  copper  and  \  zinc 
to  form   brass.     Tin  and  copper  form  very  various   alloys, 
according  to  the  proportions   employed :  90  copper  and  10 
tin  form    speculum  metal,  which  is  as  brittle   as  glass  and 
almost  white.     The  alloys  of  mercury  with  other   metals 
are    called    amalgams.     The    fusibility  of  alloys    is   often 
greater   than   that  of   the   constituent  metals.      Newton's 
fusible  metal,  an  alloy  of  5  parts  lead,  3  of  tin,  and  8  of 
bismuth,  is  an  example  of  this  fact.     Lead  fuses  at  617°, 
bismuth  at  509°,  and  tin  at  442°,  while  Newton's  alloy  fuses 
at  203°. 

Chemical  Relations  of  the  Metals. 

474.  The  metals,  as  already  stated,  are  positive  electrics. 
Their  affinity  for  oxygen  is  universal,  but  various  in  degree. 
Sodium,  potassium,  magnesium,  and  generally  the  metallic 
bases  of  the  alkalies  and  earths,  have  such  an  avidity  for 
oxygen,  that  they  pass  at  once  to  the  condition  of  oxyds  on 
contact  with  air.     Iron,  zinc,  copper,  &c.,  are  very  slowly 

How  produced  by  art?     What  rnetals  are  volatile  ?     What  is  welding? 

473.  What  are  alloys?  What  are  amalgams?    What  of  Newton  s  aietal  ? 

474.  What  are  the  chemical  relations  of  the  metals  ? 


284  METALLIC   ELEMENTS. 

oxydized,  and  are  soon  covered  by  a  coat  of  oxyd,  -which 
protects  the  metal  from  further  action.  Gold,  platinum, 
and  silver,  on  the  contrary,  resist  the  action  of  oxygen  per- 
fectly, and  are  called,  from  their  unalterable  nature,  noble 
metals. 

The  metallic  oxyds  may  be  divided  into  three  classes  :— 

1.  Basic  oxyds,  which  include  the  protoxyds  generally, 
as  potash,  soda,  lime,  and  protoxyd  of  iron.     Basic  oxyds 
unite  readily  with  acids  to  form  crystallizable  salts.     Their 
formula  is  RO. 

2.  Acid  oxyds,  which  themselves  form  salts  with  powerful 
bases,  and  rarely,  if  ever,  combine  with  other  acids.  Chromic 
acid  Cr03,  manganic  acid  Mn03,  and  other  metallic  acids 
are  examples.     Their  usual  formula  is  R03  or  R03. 

3.  Neutral  or  indifferent  oxyds,  which,  like  alumina  A1303, 
may  form  salts  with  either  powerful  acids,  or  energetic  bases. 
Their  formula  is  R303. 

475.  Besides  these  there  are  oxyds  which  unite  neither 
with  acids  nor  bases  without  change,  and  others  which  seem 
themselves  to  be  true  salts.  Of  the  first  the  common  peroxyd 
of  manganese  is  an  example,  Mn03.  Heated  with  sulphuric 
acid  it  is  decomposed,  oxygen  is  evolved,  (276,)  and  sulphate 
of  protoxyd  of  manganese  is  formed,  MuO.S03.  Suboxyd 
of  lead  PbaO  in  contact  with  acids  is  also  transformed  into 
metallic  lead  and  protoxyd  of  lead. 

Of  the  saline  oxyds  we  have  examples  in  the  oxyds  of 
manganese,  iron,  and  chromium,  whose  general  formula  is 
R304.  In  these  compounds  two  oxyds  of  the  same  metal 
form,  as  it  were,  respectively,  acid  and  base,  and  we  may 
write  their  formulae  RO.Ra03.  Magnetic  iron  is  an  instance. 

Certain  metals  form  a  great  number  of  compounds  with 
oxygen,  as  iron,  manganese,  and  chromium,  whose  oxyds 
may  be  represented  by  the  general  formulae — 

K  0  the  protoxyd,  forming  a  powerful  base. 

li^Oi  (sesquioxyd,)  a  feeble  base,  or  neutral,  but  acting  not  as  an  acid. 

K  Oa  the  binoxyd,  neither  base  nor  acid,  but  decomposed  by  acids. 

RS04  a  saline  compound,  whose  true  constitution  is  RO.RjOj. 

R  Oa  a  metallic  acid ;  and  also 

R.jOi  a  hyper-acid. 

What  their  affinity  for  oxygen  ?  How  are  the  oxyds  divided  ?  What 
are  basic  ?  What  acid  ?  What  neutral  ?  Give  their  general  formulas. 
What  other  two  classes  are  named?  Give  an  example  of  the  first.  475. 
Give  examples  of  saline  oxyds.  Give  the  general  formulae  for  the  oxydi 
of  iron,  manganese,  and  chromium. 


SALTS.  285 

Other  metals,  as  arsenic  and  antimony,  have  no  prot- 
oxyds  and  form  only  strong  acids  with  oxygon,  by  which 
feature  they  strongly  resemble  some  of  the  metalloids. 

476.  The  chlorids,  bromids,  iodids,  sulphurets,  &c.  of  the 
metals  bear  a  very  striking  analogy  in  composition  to  the 
oxyds  of  the  same  metals.     So  true  is  this,  that  knowing 
what  oxyds  a  given  metal  forms,  we  can  almost  certainly 
tell  what  the  composition  of  its  sulphurets,  chlorids,  &c.  will 
be.    Thus  the  oxyds  of  iron  being  FeO  and  Fe0303,  we  find 
that  the  sulphurets  of  the  same  metal  are  FeS  and  Fe3S3, 
and  the  chlorids  FeCl  and  FeaCl3.     It  might  be  inferred 
from  this  statement  that  where  these  metallic  bodies  unite 
with  acids  to  form  salts,  there  would  be  the  same  conformity 
among  them  that  is  found  among  their  bases,  and  such  we 
find  to  be  the  fact. 

Salts. 

477.  A  salt,  as  usually  understood,  is  a  compound  formed 
by  the  union  of  two  binary  compounds,  which  stand  to  each 
other  as  electro-positive  and  electro-negative,  or  as  base  and 
acid.     The  bases  result  always  from  the  union  of  a  metal 
with  a  metalloid ;  the  acids  usually  are  derived  from  the 
union  of  two  metalloids.      For  example,  sulphate  of  soda 
contains  for  base,  soda  (NaO,)  formed  from  the  metal  sodium 
and  the  metalloid  oxygen,  while  the  sulphuric  acid  results 
from  the  union  of  the  two  metalloids,  oxygen  and  sulphur. 
The  salts  of  metallic  acids,  as  just  explained,  (475,)  constitute 
an  exception,  as  the  metal  is  present  alike  in  acid  and  base. 

478.  Salts  are  formed  only  between  members  of  the  same 
class,  that  is  oxygen  acids  unite  with  oxygen  bases,  chlorine 
acids  with  chlorine  bases,  sulphids  with  sulphids,  &c.,  as  sul- 
phuric acid  with  oxyd  of  iron  to  form  sulphate  of  protoxyd 
of  iron. 

On  the  other  hand,  compounds  belonging  to  different  series, 
either  do  not  unite  at  all,  or  they  mutually  decompose  each 
other.  Thus,  sulphuric  acid  cannot  unite  with  sulphuret  of 
potassium,  a  sulphur  base,  but  mutual  decomposition  occurs, 
sulphydric  acid  escapes,  and  sulphid  of  potassium  is  formed. 

What  metals  have  no  protoxyds  ?  To  what  are  these  affined?  476. 
What  analogy  have  the  chlorids,  bromids,  &c.  of  the  metals  ?  477  What 
is  a  salt  ?  How  are  bases  formed  ?  How  the  acids  ?  Give  an  example. 
What  are  exceptions  ?  478.  Between  what  are  salts  formed  ?  How  do 
jompounds  of  different  classes  act  together?  Give  examples. 


286  METALLIC   ELEMENTS. 

Or  if  chlorohydric  acid  and  oxyd  of  potassium  are  brought 
together,  chlorid  of  potassium  and  water  result;  thus, 
KO+HCl^HO+KCl. 

479.  Neutral  salts  are  formed,  when  there  are  as  many 
equivalents  of  acid  engaged,  as  there  are  of  oxygen  in  the 
base  itself.    Thus,  potash  KO  has  one  equivalent  of  oxygen 
and  demands,  to  form  neutral  sulphate  of  potash  (KO.SO3) 
one  equivalent  of  sulphuric  acid.  But  one  equivalent  of  SO, 
contains  three  times  as  much  oxygen  as  there  is  in  the  base, 
and  this  is  true  of  all  the  neutral  sulphates.     The  nitrate 
of  potash  contains  five  atoms  of  oxygen  in  the  acid  to  one  in 
the  base,  and  so  on. 

The  same  is  true  also  of  those  acids  whicn  contain  no 
oxygen,  as  the  chlorohydric,  provided  the  metallic  oxyd  dis- 
solves in  chlorohydric  acid  without  the  evolution  of  chlorine. 
For  example,  peroxyd  of  iron  dissolved  in  chlorohydrie  acid 
produces  water  and  a  perchlorid  of  iron :  3HC1  and  Fe^Og 
giving  rise  to  3  HO  and  Fe3Cl3. 

480.  The  binary  compounds  of  chlorine,  iodine,  &c.,  with 
many  of  the  metals,  particularly  those  of  the  alkaline  class, 
have  iu  an  eminent  degree  the  properties  of  salts.     Among 
them  we  recognize  particularly,  the  chlorid  of  sodium,  or 
common  salt,  which  is,  so  to  speak,  the  parent  of  all  salts. 
If   the  definition  of  a  salt,  just  given,  (477,)  be  rigidly 
enforced,  these  bodies  cannot  be  called  salts,  since,  accord- 
ing to  that  view,  a  salt  is  a  compound  of  two  binary  com- 
pounds, forming  a  quaternary  compound,  (245.)     To  avoid 
this  difficulty,  two  classes  of  salts  have  been  instituted,  the 
first  of  which  includes  all  those  binary  compounds  which, 
like  common  salt,  have  a  metallic  base  in  direct  union  with 
a  salt-radical ;  and   the  second  includes  those  salts  which, 
like  sulphate  of  soda,  are  supposed  to  be  constituted  of  the 
oxyd  of  the  metal  and  of  an  oxygen  acid.     The  first  have 
been   called    the  haloid*  salts,  and  the    second  the  oxy- 
salts. 


479.  How  are  neutral  salts  formed?  What  of  sulphate  of  potash?  What 
is  the  oxygen  ratio  in  the  sulphates  ?  How  in  case  of  chlorohydric  acid  ? 
480.  What  is  said  of  binary  compounds  of  chlorine,  <fec.,  with  metals? 
What  of  common  salt?  What  two  classes  of  salts  are  named  ?  What  is 
meant  by  salt-radical  ?  What  by  haloid  salts  ? 


*  From  hah,  sea-salt,  and  eidos,  in  the  likeness  of. 


SALTS.  28? 

The  term  salt-radical  includes  all  the  members  of  the 
oxygen  group  except  oxygen  itself,  and  also  those  com- 
pound bodies  which,  like  cyanogen,  act  the  part  of  ele- 
ments. 

481.  In  stating  the  constitution  of  sulphuric  acid,  (320,) 
it  will  be  remembered  that  the  expression  S04-|-H  was  stated, 
in  the  view  of  some  chemists,  to  be  equivalent  to  the  com- 
mon formula  S03-f-HO.     It  is  claimed  that  allthehydrated 
acids  are  in  reality  compounds  of  hydrogen  with  a  similar 
radical,  and  accordingly  nitric  acid  will  be  N06-j-H>  or  cor- 
responding to  chlorohydric  acid  C1H.     One  principal  objec- 
tion to  this  view  is,  that  these  hypothetical  radicals  have  in 
general  never  been  isolated.     It  is,  however,  true  that  those 
acids  which  are  capable  of  existing  dry  and  in  a  separate 
state,  as  sulphuric,  (S03,)  phosphoric,  (P05,)  nitric,  (N05.) 
and  carbonic,  (C03,)  are  not  acids  as  long  as  they  remain 
dry;  and  although  they  form  compounds  with  dry  ammonia, 
that  these  compounds  are  not  salts.     Sir  Humphry  Davy 
long  ago  suggested  that  hydrogen  was  the  real  acidifying 
principle  in  all  acids. 

482.  If  the   salt-radical  theory  is    finally  adopted,  all 
acids  must  be  considered  as  hydrogen  acids,  and  all  salts  as 
haloid  salts.     For  example,  let  us  take  two  common  saline 
bodies  and  present  them  according  to  these  two  views. 

Old  view.  New  view. 

Sulphate  of  zinc  ZnO  4-  S03 Zn-J-SO^ 

Nitrate  of  soda  Na04-N05 Na-J-N06 

According  to  the  new  view,  when  an  acid  dissolves  a 
metal,  there  is  no  necessity  for  supposing  water  to  be  decom- 
posed. The  metal  takes  the  place  of  the  hydrogen,  and 
the  latter  is  given  off  in  a  gaseous  form ;  or  if  the  oxyd  of 
the  metal  is  used,  the  oxygen  and  hydrogen  unite  to  form 
water,  and  no  effervescence  ensues. 

The  apparent  simplicity  of  this  view  renders  it  attractive, 
and  it  has  been  most  warmly  supported  by  Profs.  Graham 
and  Liebig,  while  in  this  country  it  has  found  an  able  op- 
ponent in  Dr.  Hare. 

481.  What  is  said  of  theformulaof  SO,?  What  view  of  acids  is  suggested? 
What  objection  is  urged?  What  is  true  of  dry  S03  <fcc.  Who  formerly 
proposed  this  view  ?  482.  What  will  be  the  constitution  of  salts  in  the 
new  view  ?  How  does  a  metal  then  enter  into  a  salt  ?  Who  support 
and  who  opposes  this  view  ? 


288  METALLIC    ELEMENTS 

The  nomenclature  of  the  salts  has  already  been  explained, 
(251 :)  we  shall  consider  the  more  interesting  salt*  under 
each  metal. 

The  order  in  which  the  metallic  bodies  are  discussed  in 
the  following  pages,  is  not  very  different  from  that  usually 
adopted  in  elementary  works. 

CLASS  I.     METALS  OF  THE  ALKALIES. 

POTASSIUM. 
Equivalent,  39-2.      Symbol,  K  (Kallum.}     Density,  -865. 

483.  History. — Potassium  was  discovered  by  Sir  Humphry 
Davy  in  1807;  at  the  same  time  with  its  congeners,  sodium, 
barium,  strontium,  and  calcium.       Before  that  time,  the 
alkalies  and  alkaline  earths  were  looked  upon  as   simple 
elementary  bodies,  and    were  so    treated   in   all  chemical 
works.     Davy  found,  on  passing  the  electric  current  from  a 
powerful  voltaic  battery  through  a  cake  of  moistened  potash, 
(oxyd  of  potassium,)  both  electrodes  being  of  platinum,  that 
violent  action  followed;  oxygen  wasevolved  with  effervescence 
at  the  positive  pole,  and  bright  metallic  globules,  like  mer- 
cury, appeared  at  the  negative  pole,  accompanied  by  hydro- 
gen gas.     Some  of  these  globules  flashed  and  burned  with  a 
violet  light  as  they  reached  the  air,  while  others  remained, 
and  were  soon  covered  with  a  white  film  that  formed  on 
their  surfaces.     These  globules  were  the  metal  potassium, 
whose    discovery  constitutes  one  of  the    most   interesting 
chapters  in  chemical  history. 

Potassium  in  combination,  chiefly  as  silicate  of  potash,  is 
widely  diffused  over  the  globe.  It  forms  a  part  of  all  fer- 
tile soils.  The  chief  source  from  which  it  is  procured  is 
the  ashes  of  hard-wooded  forest-trees,  which  take  it  up  from 
soils  on  which  they  grow.  It  is  also  present  in  sea-water, 
as  chlorid  of  potassium,  and  is  consequently  found  in  the 
ashes  of  sea-plants. 

484.  Preparation. — The    expensive    and    troublesome 
method  of  procuring    this  metal    by  galvanism,  has  been 


What  is  the  nomenclature  of  the  salts  ?  483.  What  is  the  symbol  and 
equivalent  of  potassium  ?  When, and  by  whom, and  how  was  it  discovered  ? 
How  is  this  metal  distributed  in  nature  ?  484.  How  is  potassium  prepared  ? 


POTASSIUM. 


289 


*c  placed  by  a  much  more  convenient  and  productive  fur- 
nace operation,  founded  on  the  decomposition  of  potasn  at 
a  white  heat  by  charcoal.  For  this  purpose  carbonate  of  pot- 
ash is  mingled  with  charcoal.  This  mixture  is  best  prepared 
by  ignited  cream  of  tartar  in  a  covered  crucible ;  a  black 
mass  is  then  obtained  commonly  known  as  black  flux,  con- 
sisting of  carbonate  of  potassa  in  intimate  mixture  with 
charcoal  derived  from  the  burning  of  the  organic  acid.  This 
mass  is  finely  powdered,  and  JQ  of  charcoal  in  small  frag- 
ments is  added.  The  mixture  is  then  placed  in  an  iron 
bottle  Y  (fig.  348)  laid  horizontally  in  the  furnace  M  Gr  C. 


Fig.  348. 

The  bottle  should  be  about  f  full,  and  well  protected  with  a 
refractory  lute  of  5  parts  fine  sand  and  one  part  fire-clay, 
laid  on  moist,  and  well  dried  in  the  sun.  The  cover  of  the 
furnace  M  admits  the  fuel,  the  draft  0  is  regulated  by  a 
damper,  and  a  temporary  front  r  n  closes  the  side-opening. 
A  short  iron  tube  a  o  connects  the  retort  with  a  copper  con- 
densing chamber  ABC  containing  naphtha,  and  supported 
on  T  P  S.  The  heat  is  gradually  raised  to  the  most  intense 
whiteness.  Decomposition  of  the  carbonate  of  potash 
ensues,  the  free  carbon  takes  the  oxygen  of  the  carbonate, 
carbonic  oxyd  (CO)  is  evolved,  and  the  potassium  distila 

Describe  fig.  348.      What  is  the  reaction  ?     Where  does  the  potassium 
collect  ? 

19 


290  METALLIC   ELEMENTS. 

over  in  metallic  globules,  which  condense  in  the  receiver  A. 
This  copper  vessel  is  constructed  of  two  parts  B  C,  as  seen  ill 
fig.  349.  The  upper  B  enters  C,  in  which  the  naphtha  is 
placed.  A  vertical  partition  c  d  divides  B 
_«•  into  two  chambers,  and  two  openings  a  b 
opposite  each  other  correspond  to  the  iron 
tube  a  o,  (fig.  348 :)  the  partition  is  also 
pierced  in  the  same  line.  The  outer  opening 
b  is  closed  by  a  cork,  and  a  glass  tube  g  is 
adapted  to  the  opening/,  (fig.  348,)  by  which 
the  oxyd  of  carbon  escapes.  This  condenser 
is  kept  cold  by  a  constant  stream  of  cold  water 
directed  on  its  surface,  and  the  collar  m  n 
lg*  '  prevents  this  from  entering  the  lower  vase  c. 
The  tube  a  o  is  very  likely  to  become  stopped  in  the  process 
by  carbon,  and,  to  avoid  this  accident,  the  iron  rod,  (fig.  350,) 

ig*^ 9  moistened  in  naphtha,  is 

introduced  at  b  from  time 
to  time  to  clear  it.     The 

potassium  collects  in  irregular  masses  in  C,  contaminated  with 
carbon  and  other  impurities,  from  which  it  is  freed  by  a 
second  distillation  in  an  iron  retort  with  a  little  naphtha,  by 
which  means  it  is  obtained  quite  pure. 

Naphtha  is  employed  in  this  process  because  it  contains 
no  oxygen,  and  does  not  suffer  any  change  from  the  action 
of  the  potassium,  which  is  always  preserved  beneath  its  sur- 
face and  out  of  contact  of  air. 

485.  Properties. — Potassium,  when  unoxydized,  is  a  white 
metal  with  a  bluish  shade  and  eminently  brilliant.  The  dull 
masses  found  in  commerce  show  these  metallic  characters  on 
the  fresh-cut  surface ;  but  the  proper  color  and  brilliancy  dis- 
appear in  the  air,  which  instantly  tarnishes  it.  Exposed  to 
the  air  it  is  gradually  converted  into  a  white,  brittle  mass, 
(potash.)  Fused  under  naphtha,  its  metallic  lustre  and  color 
are  beautifully  seen ;  and  a  small  quantity  may  thus  be  forced 
between  two  test  tubes,  fitting  closely  the  one  within  the  other, 
so  as  to  exhibit  an  extended  white  or  bluish-white  metallic 
surface,  that  may  be  preserved  indefinitely  under  naphtha. 
At  32°  it  is  brittle  and  crystalline,  at  60°  soft  and  yielding 
to  the  fingers,  between  which  it  may  be  moulded  and  welded. 

Describe  fig.  349.  What  precautions  are  required?  Why  is  naphtha 
used  ?  485.  What  are  its  properties  ?  How  is  its  metallic  lustre  seen  ? 


COMPOUNDS   OF   POTASSIUM.  291 

Heated  in  air  it  takes  fire  and  burns  with  a  violet-colored 
flame.  At  151°  it  melts,  and  below  redness  it  may  be  dis- 
tilled unchanged  in  vessels  free  from  oxygen. 

Its  density  is  only  -865,  being  the  lightest  metal  known. 
Consequently  it  floats  on  water,  which  it  instantly  decom- 
poses; appropriating  its  oxygen  to  form  oxyd  of  potassium, 
while  the  liberated  hydrogen  burns,  with  a  portion  of  the 
volatilized  metal,  with  a  beautiful  violet-colored  flame.  If  this 
experiment  is  conducted  on  a  vase  of  water 
reddened  by  a  vegetable  color,  (fig.  351,)  the 
alkali  produced  changes  this  color  to  blue  or 
green.  The  heat  produced  in  this  experiment 
is  sufficient  to  fuse  the  potassium,  which  as- 
sumes immediately  a  spherical  form  and  bril- 
liant lustre,  and  is  rapidly  driven  over  the 
surface  of  the  water  by  the  steam  and  vapors  Fis-  351- 
produced  about  it,  forming  altogether  Jne  of  the  most  pleas- 
ing and  instructive  of  chemical  experiments.  If  the  quan- 
tity of  potassium  exceeds  a  few  grains,  the  heat  produced 
by  its  action  with  the  water  causes  an  explosion,  projecting 
the  burning  metal  in  all  directions.  An  irritating  cloud  fills 
the  air,  which  is  a  portion  of  the  alkali  (potash)  volatilized 
by  the  heat. 

486.  The  uses  of  potassium  are  confined  to  the  laboratory, 
where,  from  its  energetic  amnity  for  oxygen,  it  is  a  powerful 
means  of  research.     By  its  means  we  are  able  to  decompose 
the  oxyds  of  aluminum,  glucinum,  yttrium,  thorium,  mag- 
nesium, and  zirconium,  and  to  obtain  the  metallic  bases  of 
these  compounds.     By  it  also,  as  before  stated,  (379,)  we 
obtain  boron  and  silicon  from  boracic  and  silicic  acids. 

Compounds  of  Potassium. 

Potassium  unites  with  all  the  members  of  the  first  three 
classes,  forming  compounds,  several  of  which  are  of  great 
importance  in  the  arts  and  in  pharmacy :  of  these  we  can 
describe  only  a  few  of  the  most  important. 

487.  There  are  two  oxyds  of  potassium,  the  protoxyd  KG 
and  the  peroxyd  K03.    When  potassium  is  heated  in  a  cur- 
rent of  dry  oxygen  it  takes  fire,  burns,  and  leaves  a  yellowish 
residue,  which  is  the  peroxyd  of  potassium.     This  substance 

What  is  its  density  ?  How  does  it  act  on  water  ?  What  causes  the 
motion?  486.  What  aro  its  uses?  487.  Name  the  oxyds  of  potassium. 


202  METALLIC   ELEMENTS. 

Dissolves  in  water,  with  the  escape  of  two  equivalents  of  oxy- 
gen, and  forms  hydrate  of  potash-solution,  KO.HO.  Heated 
with  twice  its  own  weight  of  potassium  in  an  atmosphere  of 
dry  nitrogen,  it  forms  dry  oxyd  of  potassium,  thus  K03-f- 
2K  =  3KO.  This  important  compound  demands  our  at- 
tention. 

488.  The  oxyd  of  potassium  KO  is  a  powerful  base,  and 
forms  a  large  class  of  salts.  With  water  it  forms  two  distinct 
hydrates,  KO.HO  and  K0.5HO,  true  salts,  of  which  caustic 
potash  KO.HO,  the  monohydrate,  is  the  one  chiefly  interest- 
ing. This  substance  is  procured  usually  by  decomposing 
pure  carbonate  of  potash,  dissolved  in  10  parts  of  water,  in 
a  clean  iron  vessel,  with  half  its  weight  of  good  quicklime, 
previously  slaked  and  mingled  with  so  much  water  as  to 
form  a  thin  paste,  called  milk  of  lime.  This  is  added  in  small 
portions  to  the  potash  solution,  while  the  latter  is  boiling,  a 
short  interval  allowed  between  each  addition  j  all  the  lime 
being  added,  the  whole  is  boiled  for  a  few  minutes,  and  then 
is  removed  from  the  fire  and  covered  up.  The  lime  displaces 
the  carbonic  acid,  forming  carbonate  of  lime  and  caustic 
potash.  Care  is  needed  to  keep  the  solution  dilute,  to  pre- 
vent the  caustic  potash  formed  from  decomposing  the  result- 
ing carbonate  of  lime.  The  success  of  the  operation  is 
determined  by  testing  a  small  portion  of  the  clear  fluid  with 
chlorohydric  acid,  which  should  occasion  no,  or  only  a  feeble, 
effervescence. 

The  clear  dilute  solution  is  drawn  off  by  a  siphon,  boiled 
away  rapidly,  (to  prevent  absorption  of  C0a  from  the  air,) 
to  an  oily  consistency  in  a  clean  iron  or  silver  vessel,  and 
finally  carried  to  low  redness.  The  carbonate  of  potash,  if 
any  remains,  then  floats  as  a  scum,  being  less  fusible  than 
the  caustic,  and  may  be  skimmed  off.  The  fused  caustic, 
turned  out  on  a  plate  of  copper  or  iron,  hardens  into  a  white 
crystalline  cake,  which  is  at  once  broken  up  and  put  in  close 
bottles.  To  insure  its  purity  from  sulphates  and  chlorids, 
(often  present  in  the  original  carbonate,)  it  is  dissolved  in 
absolute  alcohol,  which  leaves  the  other  salts  undissolved. 
The  alcoholic  solution  is  decanted,  distilled  in  a  retort,  and 
evaporated  in  a  silver  capsule,  fused  and  cast  as  before.  No 
degree  of  heat  will  expel  the  equivalent  of  water  which 


How  are  they  obtained  ?    488.  What  of  KO  ?    What  is  KO.HO  ?    How 
procured?    What  the  reaction ?    How  freed  from  sulphates,  <fcc.? 


COMPOUNDS   OF   POTASSIUM.  293 

this  hydrate  retains.  Pure  caustic  potassa  is  also  obtained 
by  decomposing  sulphate  of  potash  solution  by  exactly  as 
much  oxyd  of  barium  as  is  required  to  saturate  it.  The  re- 
action is  KO.S034-BaO.HO  =  BaO.S03+KO.HO. 

489.  The  hydrate  of  potash  is  a  white  solid,  with  a  crys- 
talline fracture.     It  has  a  great  avidity  for  moisture  and  is 
soluble  in  half  its  weight  of  water.     Exposed,  it  forms  a  so- 
lution in  the  moisture  of  the  atmosphere.     It  is  a  most 
powerful  base,  decomposing  by  fusion  the  silicates  of  nearly 
all  metallic  oxyds.     Cast  in  cylinders,  it  forms  the  caustic 
potassa  of  surgeons,  for  which  use  the  mixture  of  caustic 
and  carbonate  of  lime  with  potassa  is  commonly  employed  in 
pharmacy,  under  the  name  of  potassa  cum  calce ;  and  the 
crude  potash  of  commerce,  cast  in  cylinders  of  a  brown  color, 
are  sold  under  the  name  of  lapis  infernalis. 

The  solution  of  caustic  potash  is  intensely  alkaline,  satu- 
rates the  most  powerful  acids,  restores  the  colors  of  redden- 
ed vegetable  blues,  and  turns  many  of  them  green.  It  has 
an  acrid  and  most  disgusting  taste,  peculiar  to  alkalies,  and, 
when  strong,  attacks  all  organic  matters,  dissolving  and  dis- 
organizing them,  feeling  for  this  reason  soapy  to  the  fingers 
on  first  contact  with  the  solution.  With  the  fats  it  forms 
soaps,  true  salts,  produced  between  the  fatty  acids  and  the 
alkaline  base.  It  dissolves  silica  in  its  soluble  form,  (382,) 
and  even  attacks,  when  concentrated,  the  glass  vessels  in 
which  it  is  kept.  It  absorbs  carbonic  acid  completely,  and 
is  employed  for  that  purpose  in  organic  analysis.  The 
moderately  concentrated  solution,  (sp.  gravity  1*2,)  as 
procured  in  the  process,  (488,)  is  sufficient  for  laboratory 
use.  Potash  is  a  fatal  corrosive  poison. 

490.  The  tests  for  the  presence  of  potash  or  its  salts  are 
chlorid  of  platinum,  an  alcoholic  solution  of  which  produces 
a  yellow  crystalline  double  salt  of  potassium  and  platinum 
in  concentrated  solutions :  perchloric,  tartaric,  and  hydro- 
fluosilicic  acids  also  form  sparingly  soluble  salts  with  potas- 
sium and  its  salts. 

491.  The  chlorid  of  potassium  KC1,  is  a  soluble  com- 
pound, crystallizing  in  cubes.     It  is  formed  when  potassium 
is  heated  in  chlorine,  and  when  potash  or  its  carbonate  is 


489.  What  are  its  properties  f  What  are  potassa  cum  calce,  and  lapia 
infernalis?  What  of  potash  solution  ?  What  does  it  absorb  ?  490.  What 
are  its  tests  ?  491.  What  is  chlorid  of  potassium  ? 


204  METALLIC    ELEMENTS. 

dissolved  in  chlorohydric  acid.  It  has  a  saline  bitter  taste, 
is  deliquescent,  and  does  not  possess  the  antiseptic  properties 
of  its  congener,  the  chlorid  of  sodium. 

The  bromid  of  potassium  KBr  is  also  a  soluble  cubical 
salt,  possessing  the  medical  properties  of  bromine.  It  is  pro- 
duced in  the  mother  liquor  of  the  salines,  (294,)  and  has 
been  sold  fraudulently  for  the  iodid  of  potassium,  which  it 
much  resembles,  but  does  not  replace  in  medical  use.  Chlo- 
rine and  the  stronger  acids  decompose  it  with  evolution  of 
bromine. 

The  iodid  of  potassium  KI,  often  called  the  hydrio- 
datc  of  potash,  is  a  compound  of  great  importance  in  medi- 
cal practice  and  in  photography.  It  occurs  in  cubical  crys- 
tals, which  are  soluble  in  2  parts  of  water  and  in  6  parts  of 
alcohol  of  .85.  It  is  obtained  when  iodine  is  dissolved  in 
potash  solution  to  saturation,  and  also  at  the  same  time  iodate 
of  potash,  (KO.I03.)  The  iodid  is  separated  by  repeated 
crystallization,  or  if  the  whole  saline  mass  is  ignited,  oxygen 
is  expelled  and  only  iodid  of  potassium  is  left.  Its  solution 
dissolves  iodine  largely  and  acquires  thereby  a  dark  color. 
Starch  paste,  as  before  stated,  is  the  appropriate  test  for  it. 
flicjtuurid  of  potassium  KF,  is  also  a  soluble  cubical  salt, 
exactly  analogous  to  the  foregoing  compounds. 

The  cyanid  of  potassium  is  described  in  the  organic 
chemistry. 

492.  The  snlpkurcts  of  potassium  are  numerous,  five  of 
which  are  described,  viz.  KS,  KS2,  KS3,  KS4,  KS5.  The 
protosulphuret  KS  is  found  in  an  impure  state,  when  an 
intimate  mixture  of  2  parts  of  sulphate  of  potash  and  1 
part  of  lamp-black  are  fused  together  in  a  crucible.  Owing 
to  the  minute  division  of  its  particles  with  the  excess  of  car- 
bon, it  forms  a  very  inflammable  mass,  which  takes  fire  on 
exposure  to  air.  This  has  been  called  a  pyrophorus,  or 
bearer  of  fire.  The  protosulphuret  of  potassium  is  also 
formed  by  saturating  a  solution  of  potassa  with  sulphydric 
acid,  which,  evaporated,  leaves  a  white  crystalline  mass. 
From  this  salt  all  the  other  sulphurets  of  potassium  may 
be  formed. 

How  different  from  chlorid  of  sodium  ?  What  of  bromid  ?  What  fraud 
has  it  served  ?  What  sources  has  it  ?  What  is  iodid  of  potassium  ?  How 
obtained?  What  importance  has  it?  492.  What  sulphurets  of  potas- 
sium are  named?  How  is  the  protosulphuret  formed?  What  is  the 
yyropherua  ? 


SALTS   OF   POTASH.  295 

The  pentasulphuret  KS5  is  produced  most  readily  by  heat- 
ing a  strong  solution  of  potassa  with  an  excess  of  sulphur. 
A  large  part  of  the  sulphur  is  dissolved,  forming  a  deep 
yellow  liquid  which  contains  pentasulphuret  of  potassium, 
and  hyposulphite  of  potassa.  The  pentasulphuret  of  potas- 
sium in  the  solid  state  has  the  old  name  of  liver  of  sulphur^ 
and  its  solution  is  used  in  diseases  of  the  skin  and  as  a  de- 
pilatory. 

493.  When  potassium  is  heated  in  dry  ammonia,  an  olive- 
green  compound  is  formed,  (K.NH3,)  which  when  heated 
evolves  ammonia  and  leaves  a  dark  gray  powder  resembling 
graphite,  which  is  a  compound  of  nitrogen  and  potassium, 
having  the  formula  KaN.     The  other  compounds  of  potas- 
sium, with  phosphorus,  carbon,  boron,  &c.,  are  comparatively 
unimportant. 

Salts  of  Potash. 

494.  The  salts  of  potash  are  numerous  and  important. 
We  shall,  however,  mention  now  only  the  carbonates,  sul- 
phates, nitrate,  and  chlorate.     As  it  will  be  altogether  im- 
possible to  give  even  the  names  of  all  the  salts  of  the  metals, 
we  must  content  ourselves  with  a  selection  of  the  most  im- 
portant and  interesting. 

495.  Carbonates  of  Potash. — There  are  three  carbonates 
of  potash,  the  neutral  carbonate  KO.C02,the  sesquicarbonate 
KO.fC02,  and  the  bicarbonate  K0.2COS. 

The  neutral  carbonate  KO.C03  is  procured  from  the  ashes 
of  plants,  and  in  an  impure  form  is  made  on  a  great  scale  in 
America,  under  the  names  of  pot  and  pearl  ashes,  which  are 
the  alkali  as  obtained  from  the  lixiviation  and  combustion 
of  the  ashes  of  forest-trees. 

The  crude  carbonate  of  potash  of  commerce  is  contami- 
nated by  silica,  sulphate  of  potash,  and  chlorids  of  potassium 
and  sodium.  The  latter  impurity  is  frequently  added  in  the 
process  of  manufacture,  either  through  ignorance  or  from 
fraudulent  motives.  The  best  potash  is  made  by  using  hot 
water  to  lixiviate  the  ashes,  in  small  leach-tubs.  The  brown 
mass  left  by  evaporating  the  lixivium  to  dryness  in  iron 

How  is  pentasulphuret  of  potassium  formed?  What  uses  has  it? 
493.  What  is  the  action  of  dry  ammonia  with  K  ?  494.  What  salts  of 
potash  are  formed?  495.  What  carbonates?  How  is  the  neutral  car- 
bonate obtained  ?  What  are  pot  and  pearl  ashes  ?  What  impurities  ha« 
the  crude  article  ?  How  does  " pearlash"  differ  from  "potash  ?" 


296  METALLIC    ELEMENTS. 

kettles  is  the  potash  of  commerce.  This  is  moderately  cal- 
cined to  burn  off  the  coloring  matter,  when  a  spongy  mass 
of  a  fine  light  blue  color  is  left,  which  is  the  pearlash. 

Several  samples  of  American  potash  examined  by  Dr.  L. 
0.  Beck,  yielded  73-6,  74-6,  75  and  76-9  per  cent,  of  car- 
bonate and  hydrate  of  potash;  from  6  to  15  per  cent,  of 
chlorids  of  potassium  and  sodium ;  with  from  1  to  15  per 
cent,  of  insoluble  matter,  consisting  of  silica  and  the  oxyds 
of  iron  and  manganese,  with  lime,  alumina,  &c.,  being  the 
ingredients  derived  from  the  inorganic  parts  of  the  plant. 

496.  The  pure   carbonate  is  obtained  by  calcining  the 
cream  of  tartar,  (acid  tartrate  of  potash,)  and  dissolving  out 
the  carbonate  from  the  coaly  mass  by  water.     The  filtered 
solution  is  evaporated  to  dryness  in  a  silver  capsule,  and  the 
salt  obtained  pure. 

The  carbonate  of  potash  has  a  strong  alkaline  taste,  turns 
blue  cabbage  or  dahlia-paper  green,  and  is  somewhat  caustic ; 
it  dissolves  in  about  twice  its  weight  of  water,  forming  a  so- 
lution, which  is  much  used  in  the  laboratory.  It  crystallizes 
with  difficulty,  and  takes  up  two  equivalents  (20  per  cenfc.) 
of  water  in  so  doing.  It  is  quite  insoluble  in  alcohol.  It  is 
a  very  deliquescent  salt,  and  must  be  kept  in  well-stopped 
bottles.  Its  solution  acts  as  a  poison  if  taken  in  a  concen- 
trated form.  It  usually  retains  a  trace  of  silica,  which  is 
soluble  in  the  concentrated  solution. 

Bicarbonate  of  Potash  K0.2C02  is  formed  by  passing  a 
stream  of  carbonic  acid  gas  through  a  cold  solution  of  car- 
bonate of  potash.  It  crystallizes  in  large  and  beautiful 
crystals,  referable  to  the  right  rhombic  system.  These 
crystals  contain  9  per  cent,  of  water  and  have  the 'formula 
K0.2COa+HO.  Four  parts  of  water  dissolve  it;  the  solu- 
tion has  an  alkaline  taste  and  reaction,  but  is  not  caustic ; 
by  heat  it  is  converted  to  the  simple  carbonate,  and  it  loses 
a  portion  of  carbonic  acid  by  solution  in  hot  water. 

497.  Alkalimetry. — The  value  of  commercial  samples  of 
the  carbonates  of  potassa  and  soda  is  determined  by  the 
process  of  alkalimetry,  which  consists  in  ascertaining  how 
much  dilute  sulphuric  acid  of  a  standard  strength  is  required 
to  neutralize,  exactly,  a  known  weight  of  the  sample  exa- 


What  is  the  composition  of  commercial  potash?  496.  How  is  pure  car- 
bonate obtained?  What  are  its  characters?  How  is  the  bicarbonate 
obtained?  What  its  form  and  character ?  497.  What  is  alkalimetry  ? 


. d  ^ 

SALTS    OP   POTASH.  297 

"*I~T"\ 

mined.     The  strength  of  the  acid  is  such  that  100 
it  by  measure  will  exactly  saturate  10  parts 
pure  alkaline  carbonate.     It  is  foreign  to  our  present  pur- 
pose to  give  the  full  details  of  this  process. 

498.  Sulphate  of  Potash,  KO.S03.— This  salt  is  prepared 
by  neutralizing  a  concentrated  solution  of  potash  by  strong 
sulphuric  acid,  added  drop  by  drop.     It  is  also  a  result  of 
many  processes  in  the  arts.     It  fuses  at  a  red  heat  without 
change.     It  is  an  anhydrous,  crystallized  salt,  which  decre- 
pitates with  heat,  and  has  a  density  of  24.  This  salt  requires 
100  parts  of  water  to  dissolve  8-36  parts  at  32°,  and  0-096 
parts  more  of  the  salt  dissolve  for  every  degree  above  that. 
It  is  one  of  the  hardest  of  the  saline  bodies.     It  is  wholly 
insoluble  in  alcohol. 

Bisulphate  of  Potash  KO.S03-f-HO.S03  is  a  result  of  the 
nitric  acid  process  (334)  when  a  double  equivalent  of  sul- 
phuric acid  is  used.  It  is  properly  a  double  sulphate  of 
potassa  and  water.  It  is  formed  also  when  sulphate  of 
potassa  is  added  to  its  own  weight  of  S03.  It  fuses  at  392° 
without  change  and  without  loss  of  water.  A  higher  heat 
expels  one  equivalent  of  sulphuric  acid.  It  is  decomposed 
by  absolute  alcohol,  leaving  KO.S03.  It  is  dimorphous, 
one  of  its  forms  being  identical  with  crystallized  sulphur. 
The  solution  is  strongly  acid,  and  acts  on  bases  nearly  as 
powerfully  as  if  potash  were  not  present.  When  this  salt  is 
exposed  to  air,  beautiful  silky  crystals,  resembling  asbestus, 
effloresce  upon  its  surface.  These  are  sesquisulphate  of 
potash  2KO.SOa-f  HO.S08. 

499.  Nitrate  of  Potassa;   Saltpetre;  Nitre;    KO.N05. 
This  important  salt  is  a  natural  product  in  the  hot  and  dry 
regions  of  India  and  South  America,  being  formed  by  the 
gradual  decomposition  of  animal  matters  in  the  soil.     It  is 
also  formed  artificially  by  heaping   together  beds  of  old 
mortar  and  earth  with  dung  and  other  animal  matters,  and 
occasionally  wetting  the  mass  with  fermenting  urine.     In 
the  Mammoth  Cave  in  Kentucky,  and  other  caverns,  the 
soil  on  the  floors  becomes  strongly  impregnated  with  nitrate 
of  lime,  which  is  decomposed  by  wood   ashes,  and  yields 

Give  ^he  principle  of  the  process.  498.  What  is  sulphate  of  KO  ? 
Give  its  properties,  &c.  Give  the  formula  for  bisulphate  of  potash. 
What  is  its  proper  name  ?  Give  its  properties.  What  is  sesquisulphate 
of  KO?  How  produced?  499.  What  is  KO.NO,?  How  formed  and 
found  ?  How  formed  artificially  ?  What  the  origin  of  the  NO.? 


208  METALLIC    ELEMENTS. 

nitrate  of  potassa.  In  all  those  cases,  the  nitre  is  obtained 
by  lixiviating  the  nitrous  earth  with  water,  evaporating  and 
crystallizing  the  solution,  redissolving  and  crystallizing  a 
second  time,  until  the  salt  is  obtained  pure.  Nitre  also 
crystallizes  from  the  juices  of  some  plants. 

It  appears  that  the  nitre  of  caverns  must  come  from  the 
union  of  the  elements  of  the  atmosphere,  under  the  influence 
of  carbonate  and  nitrate  of  ammonia,  always  found  to  some 
extent  in  the  air.  Rain  water  usually  contains  a  trace  of 
nitrate  of  ammonia,  produced,  as  is  supposed,  by  the  union 
of  the  elements  of  the  air  by  natural  electricity,  (§331  and 
fig.  252.) 

500.  Properties. — Nitre   crystallizes   in    long,   six-sided 
prisms,  with    dihedral   summits,   derived   from    the   right 
rhombic  prism.     Its  density  is  1-94.     It  is  anhydrous,  and 
fusible  at  about  GGO°  :  at  a  higher  temperature  it  is  decom- 
posed, yielding  oxygen  and  nitrite  of  potassa.  It  is  unaltered 
in  the  uir  and  insoluble  in  alcohol,  but  dissolves  in  about  3 
parts  of  water  at  60°.  In  hot  water  it  is  much  more  soluble, 
100  parts  of  water  at  200-6°  dissolving  236  parts  of  the  salt. 
Its  solution  has  a  cooling  taste,  and  is  slightly  bitter.     It 
is  an  antiseptic,  and  is  used   in  the  brine  for  preserving 
meats,  to  give  a  fine  red  color  to  the  flesh. 

Nitrate  of  potassa  (as  well  as  nitrate  of  soda)  has  been 
much  esteemed  as  a  manure.  It  is  employed  also  to  pro- 
cure oxygen,  (275,)  and  the  best  nitric  acid  is  made  from 
it,  (334.) 

501.  The  great  quantity  of  oxygen  contained  in  nitre, 
and  the  ease  with  which  it  parts  with  it,  render  it  a  power- 
ful means  of  oxydation.    Fused  on  a  coal  it  deflagrates  bril- 
liantly.   It  is  the  chief  constituent  of  gunpowder,  imparting 
oxygen  to  the  carbon  and  sulphur  in  that  mixture,  to  form 
with  explosive  energy  those  gases  which  are  generated  by 
the  combustion  of  the  materials.     It  is  also  much  used  in 
all  pyrotechnic  mixtures,  as  well  as  to  deflagrate  and  scorify 
metals.  The  surface  of  silver-ware  is  often  scorified  by  nitre, 
which  burns  out  the  alloyed  copper,  and  leaves  a  surface  of 
pure  silver.     Good  gunpowder  is  composed  very  nearly  of 
1  equivalent  of  nitre,  3  of  carbon,  and  1  of  sulphur.     Thus 


How  is  it  procured  from  the  nitrate  of  lime  ?  500.  What  are  the  pro 
perties  of  nitre?  501.  What  renders  nitre  a  valuable  reagent?  What  i« 
an  antiseptic  ?  Of  what  is  nitre  the  chief  constituent  ? 


SALTS   OP  POTASH.  299 

the  powder  used  in  war  has  the  following  composition  in 
different  countries  :  — 


French'     1>russian- 

Sulphur  .............  11-9  ......  12-5  ......  11-5  ......  10  .........  9  .........  9-9 

Charcoal  ............  13-5  ......  12-5  ......  13'5  ......  15...  ......  16  .........  14-4 

Nitre  ................  74-6  ......  75-  ......  75-  ......  75  .........  75  .........  75-7 

Much  of  the  explosive  energy  of  gunpowder  depends  on 
its  granulation  ;  a  fine  dust,  of  the  same  composition  with 
powerful  powder,  burns  with  a  rapid  deflagration,  but  with- 
out explosion.  The  constitution  of  gunpowder  is  varied 
according  to  the  use  for  which  it  is  intended.  Thus,  20 
sulphur,  18  charcoal,  and  62  nitre,  are  used  for  blasting- 
powder  in  mines,  and  its  combustion  may  be  rendered  still 
slower  by  mixing  it  with  several  times  its  bulk  of  sawdust. 
The  effect  then  is  more  powerful  in  moving  large  masses  of 
rocks. 

The  gases  formed  in  the  combustion  of  gunpowder  are 
carbonic  acid  and  nitrogen,  while  sulphuret  of  potassium 
remains  as  a  solid  residue.  The  combustion  of  a  squib,  or 
moist  gunpowder,  gives  a  much  more  complicated  result; 
nitric  oxyd,  sulphuretted  hydrogen,  carbonic  acid,  carbonic 
oxyd,  nitrogen,  and  other  products  being  formed. 

502.  Chlorate  of  Potash,  KO.C105.  —  This  salt  is  the  salt 
already  named  (275)  as  the  best  source  of  pure  oxygen  gas. 
It  is  formed  by  passing  chlorine  gas  through  a  strong  solution 
of  carbonate  of  potash,  chlorate  of  potash  and  chlorid  of  po- 
tassium being  formed,  the  chlorate  being  easily  crystallized 
out  by  its  less  solubility.     The  carbonic  acid  escapes.     The 
reaction  is  between  6KO.C03  +601  =  5KC1  -j-  KO.C1CK 
+  6C03. 

503.  Properties.  —  Chlorate  of  potash  crystallizes  in  flat, 
pearly  tables,  referable  to  the  oblique  rhombic  prism.    Water 
at  32°  dissolves  only  3-3  parts  in  100;  at  60°  only  6  parts, 
while  boiling  water  dissolves  nearly  60  parts;  it  is  therefore 
much  more  soluble  in  hot  than  in  cold  water.     It  is  insolu- 
ble in  alcohol.     Its  taste  is  cooling  and  disagreeable,  resem- 
bling nitre.     It  fuses  at  750°  ;  above  that  heat,  oxygen  is 
given  off,  and  chlorid  of  potassium  left  behind.    It  is  a  most 

What  is  the  constitution  of  gunpowder  in  different  countries  ?  On  what 
does  its  explosive  energy  depend  ?  What  are  the  products  of  its  combus- 
tion ?  If  wet,  what  are  they?  How  is  blasting-powder  made  more  effi- 
cient ?  502.  What  is  chlorate  of  potassa,  and  how  formed  ?  503.  What 
are  its  properties  ? 


?>00  METALLIC   ELEMENTS. 

energetic  oxydizing  agent.  It  forms  explosive  mixtures  with 
Dearly  all  combustible  bodies. 

504.  With  sulphur  and  charcoal  it  forms  a  compound  that 
explodes  by  friction,  or  by  a  drop  of  sulphuric  acid,  and  was 
formerly  much  used  in  the  preparation  of  friction  matches. 
With  sulphur  alone,  it  detonates  powerfully  when  wrapped 
in  a  paper  and  struck  by  a  hammer.  With  phosphorus  its 
reaction  is  extremely  violent ;  a  deafening  explosion  follows 
the  slightest  compression  of  the  ingredients,  and  burning 
phosphorus  is  projected  in  all  directions.  Its  large  con- 
sumption in  the  preparation  of  matches  has  rendered  it  a 
cheap  salt. 

All  attempts  to  form  a  gunpowder  of  chlorate  of  potash 
have  failed,  the  action  of  the  mixture  being  so  violent  as  to 
rend  asunder  the  arms  employed.  A  mixture  of  sugar  and 
chlorate  of  potash  is  instantly  inflamed  by  a  drop  of  sulphu- 
ric acid,  and  burns  with  the  violet  color  which  belongs  to  all 
the  salts  of  potassium. 

The  characters  of  the  salts  of  potash  are  the  same  with 
reagents  as  those  of  potassa  before  given,  (490.)  The  salts 
of  the  alkalies  are  distinguished  from  all  other  metallic  salts 
by  yielding  no  precipitate  to  an  alkaline  carbonate.  All  the 
potash  salts  form  with  sulphate  of  alumina  a  crystalline 
double  sulphate  of  potassa  and  alumina — common  alum — 
crystallizing  in  octahedrons. 


SODIUM. 
Equivalent,  23.     Symbol,  Na.     Density,  -972. 

505.  Sodium  wag  discovered  by  Davy  soon  after  the  dis- 
covery of  potassium,  and  in  the  same  way.  It  is  now  pre- 
pared by  a  process  quite  similar  to  that  already  described 
(484)  for  potassium ;  the  carbonate  of  soda  being  used  in 
place  of  the  carbonate  of  potassa. 

This  metal  forms  more  than  40  parts  in  100  of  common 
salt,  and  is  also  frequent  in  various  combinations  in  the 
mineral  kingdom.  The  ashes  of  sea-plants  afford  crude 


What  its  solubility?  What  is  its  reaction  with  combustibles?  504. 
Why  not  fit  for  gunpowder?  What  color  does  it  burn  with?  What  are 
the  characters  of  potash  salts  ?  What  compound  do  they  form  with 
alumina?  505.  Give  the  history  and  distribution  of  sodium.  How 
procured  ? 


SODIUM.  301 

carbonate  of  soda,  in  place  of  the  carbonate  of  potash  pro- 
cured from  land-plants. 

506.  Sodium  is  a  white  metal,  with  a  silvery  brilliancy, 
and  much  resembles  potassium  in  its  general  properties.    Ita 
color  is  much  whiter  than  that  of  potassium,  and  its  dis- 
position to  tarnish  less.    Its  density  is  '972,  and  it  melts  at 
194°.     At  common  temperatures  it  is  harder  than  potas- 
eium,  but  is  easily  moulded  in  the  fingers.     It  does  not  in- 
flame on  cold  water,  unless  in  masses  of  considerable  size, 
but  moves  about  rapidly,  fused  into  a  brilliant  sphere,  until 
it  is  all  consumed.     It  may  be  alloyed  with  potassium  by 
simple  pressure,  and  is  then  inflamed  on  water,  or  alone  on 
hot  water,  burning  with  a  bright  yellow  light,  characteristic 
of  sodium,  and  strongly  contrasted  with  the  violet  color  of 
the  potassium  flame.     The  same  color  is  seen  when  a  piece 
of  soda-glass,  or  any  mineral  containing  soda,  is  held  in  the 
flame  of  the  blowpipe;  the  flame  is  instantly  tinged  yellow. 
Exposed  to  the  air,  sodium  soon  falls  to  a  white  powder  of 
oxyd  of  sodium. 

The  compounds  of  sodium  are  so  similar  to  those  of  potas- 
sium that  we  can  pass  them  with  a  brief  notice. 

The  oxyds  of  sodium  and  their  hydrates  are  the  same  in 
composition  as  those  of  potassa. 

507.  The  hydrate  of  soda,   or  caustic   soda,  NaO.HO, 
is  procured  by  decomposing  the  carbonate  by  quicklime,  in 
the  same  manner  as  has  already  been  described  for  caustic 
potash,  (488.)    It  is  a  powerful  alkaline  base,  very  soluble  in 
water,  and  deliquescent  in  moist  air.      It   forms  a  white 
crystalline  cake,  resembling  potassa.     It  is  a  corrosive  and 
energetic  poison.     All  its  salts  are  soluble,  which  renders  it 
somewhat  difficult  to  detect  its  presence  in  solution. 

508.  Chlorid  of  Sodium,  or  Common  Salt,  NaCL— This 
familiar  and  abundant  substance  is  too  well  known  to  need 
much  description.      It  is  formed  when  sodium  burns  in 
chlorine  gas,  as  well  as  when  soda,  or  its  carbonate,  is  neu- 
tralized by  chlorohydric  acid.     In  Poland,  Austria,  Spain, 
Sicily,  and  Switzerland,  extensive  beds  of  pure  rock-salt  are 
found,  which  are  regularly  mined.      Common  salt  forms 
about  27  of  every  1000  parts  of  sea-water,  and  in  warm 

506.  What  its  properties?  What  is  the  color  of  its  flame?  What  of 
its  compounds  ?  507.  What  is  NaO.HO  ?  How  procured  ?  Give  its  pro- 
perties. What  of  its  salts?  508.  What  is  NaCl?  How  artificially 
formed  ?  How  found  in  nature  ? 


302  METALLIC   ELEMENTS. 

climates,  especially  In  the  West  Indies,  sea-water  is  evapo- 
rated in  large  quantities  by  the  sun's  heat,  to  obtain  salt. 
Numerous  saline  springs  are  found  in  New  York,  Ohio, 
Kentucky,  and  other  places  in  this  country,  which  afford 
vast  quantities  of  salt  by  evaporation.  The  brine  springs  iu 
Onondaga  county,  New  York,  are  among  the  most  valuable, 
and  have  been  worked  since  1789.  Their  water  contains  one- 
seventh  part  of  dry  salt.  The  water  of  the  Great  Salt  Lake, 
in  Deseret,  contains  200  parts  of  salt  in  1000,  or  over  Jth 
of  its  weight.  This  salt  is  nearly  pure.  The  Dead  Sea  has 
a  still  greater  concentration,  (§  544.) 

Common  salt  crystallizes  in  cubes,  which  are  anhydrous, 
and  crackle,  or  decrepitate,  when  heated,  owing  to  water 
mechanically   entangled   in    them.      Salt    forms    singular 
hopper-shaped  crystals,  (fig.  352.)     These  are  produced  on 
the  surface  of  the  evaporating  brine,  and 
grow  by  increase  of  the  outer  edges,  as 
gravity  sinks  them  constantly,  a  trifle 
below  the  surface  of  the  fluid,  each  ad- 
ditional row  of  particles  being  built  upon 
Fig.  352.  the  upper  and  outer  edge  of  the  last.    It 

requires  2*7  parts  of  water  for  its  solution,  and  it  is  equally 
soluble  in  hot  and  cold  water.  In  pure  alcohol  it  is  scarcely 
at  all  soluble.  Its  density  is  2-557.  It  fuses  at  redness, 
and  sublimes  in  vapor  at  a  higher  temperature.  It  is  em- 
ployed for  this  reason  to  glaze  earthenware,  since  its  vapor 
is  decomposed  by  the  oxyd  of  iron  of  the  clay,  chlorid  of 
iron  being  driven  off,  while  soda  unites  with  the  silica  of 
the  clay  to  form  the  glaze. 

The  bromid,  iodid,  and  sulpJiurcts  of  sodium  resemble  the 
corresponding  compounds  of  potassium,  and  the  two  former 
likewise  crystallize  in  cubes. 

509.  Neutral  Sulphate  of  Soda,  Glauber's  Salt,  NaO. 
S03-f-(10HO).—  This  familiar  salt  is  found  abundantly  in 
commerce  in  large  crystals,  which  contain  more  than  half 
their  weight  of  crystallization  water,  viz  : 

"I  eq.  anhydrous  sulphate  of  soda 71  44*10 

10    "     water   90  55-90 

1    "     crystallized  sulphate  of  soda 161  100*00 

How  much  in  sea  water  ?  in  salines  ?  in  the  Great  Salt  Lake  ?  What 
of  its  crystallization  ?  How  are  the  hoppers  formed  ?  How  soluble  ? 
Its  density  ?  Why  used  to  glaze  pottery  ?  509.  Give  the  formula  for 
Glauber's  salt.  What  is  its  composition  ? 


COMPOUNDS   OP   SODIUM. 


303 


210 


It  fuses  at  a  moderate  temperature  in  its  own  water 
leaves,  on  heating,  anhydrous  sulphate  of  soda. 
to  air,  the  crystals  of  Glauber's  salt  efflo-  93° 

resce,  and  fall  to  powder,  from  loss  of  322 
water.  If  its  solution  is  heated  above 
93°,  anhydrous  sulphate  of  soda  is 
thrown  down.  The  solubility  of  sul- 
phate of  soda  presents  very  remarkable 
anomalies.  Below  32°  it  is  slightly 
soluble.  At  32°,  12  parts  dissolve  in  100 
parts  of  water  :  the  quantity  dissolved 
increases  very  rapidly  with  the  tempe- 
rature up  to  93°,  which  presents  the 
maximum  of  solubility  of  the  salt,  being 
322  parts  in  100  of  water.  Above  that 
point  the  solubility  diminishes  rapidly 
with  each  increment  of  temperature, 
until  at  218°  it  has  diminished  to  210 
parts  in  100  of  water.  The  line  ABC  32o  218° 

on    the   diagram  (fig.    353)  illustrates  Fig.  353. 

the  relations  of  solubility  and  temperature  in  this  salt  at  a 
glance.  The  vertical  divisions  0  to  0'  register  the  range  of 
temperature  from  32°  to  218°;  the  horizontal  ones  0  (Vindi- 
cate the  degree  of  solubility,  which  reaches  322  parts  at  93°. 
The  curve  of  solubility  then  descends  from  B  to  C,  when 
210  parts  are  dissolved  at  218°.  The  cause  of  this  sud- 
den diminution  of  solubility,  is  the  decomposition  of  the 
hydrous  salt  in  solution  at  that  heat,  and  the  precipi- 
tation of  a  portion  of  anhydrous  sulphate  of  soda.  A  solu- 
tion of  Glauber's  salts  saturated  at  boiling  heat  in  a  vessel 
capable  of  being  corked  while  boiling,  and  suifered  to  cool, 
will  often  crystallize  completely  on  withdrawing  the  cork, 
a  change  from  the  fluid  to  the  solid  state  occasioned  by  the 
concussion  of  the  air.  The  same  thing  happens  if  a  small 
crystal  is  dropped  into  a  saturated  solution  of  the  salt, 
(41.) 

Sulphate  of  soda  is  a  familiar  aperient.  In  the  arts,  its 
chief  use  is  in  the  preparation  of  carbonate  of  soda,  as  will 
be  presently  described.  It  is  a  result,  on  a  large  scale,  of 


How  does  it  fuse  ?  How  if  exposed  ?  How  does  it  dissolve  in  water 
at  different  temperatures  ?  What  is  its  curve  of  solubility  ?  Describe 
the  diagram  353.  How  is  its  solution  in  vacuo  crystallized  ?  What  is  its 
use  in  the  arts  ? 


SOI  METALLIC   ELEMENTS. 

the  preparation  of  chlorohydric  acid,  (426.)  The  other 
sulphates  of  soda  require  no  mention  at  present.  The  solu- 
tion of  sulphate  of  soda  (12  parts)  in  strong  chlorohydric 
acid  (10  parts)  produces  cold  enough  to  freeze  a  considerable 
quantity  of  water  in  summer. 

510.  Carbonate  of  Soda,  NaO.C03. — Soda  replaces  in  the 
ashes  of  sea-plants  the  potash  found  in  those  of  land- 
plants.  Hence,  formerly,  the  carbonate  of  soda  of  com- 
merce was  procured,  almost  exclusively,  from  the  ashes 
of  sea-weeds.  This  salt  is  now  obtained  entirely  from 
common  salt  by  the  process  of  Leblanc,  which  will  be  briefly 
described.  This  process  depends  on  the  fact  that  when 
sulphate  of  soda,  carbonate  of  lime,  and  carbon  are  heated 
together,  carbonate  of  soda,  oxysulphate  of  lime,  and  oxyd 
of  carbon  are  the  products.  The  reaction  is  between  2  eq. 
of  sulphate  of  soda,  3  of  carbonate  of  lime,  and  9  of  carVon; 
thus,  2(NaO.S03)  -f  3  (CaO.C02)  +  90  =  2  (NaO.C03)  + 
(2CaS.CaO)-flOCO.  The  oxysulphuret  of  calcium  is 
wholly  insoluble  in  water,  which  takes  out  from  the  pulve- 
rized mass  only  carbonate  of  soda.  This  operation  is  pre- 
pared in  a  reverberatory  furnace  constructed  like  the  section 
seen  in  fig.  354.  The  parts  A  and  B  receive  the  mingled 


Fig.  354. 

materials,  (1000  parts  of  anhydrous  sulphate  of  soda,  1040  of 
chalk,  and  530  of  charcoal  powder.)  The  fire  on  the  grate 
F  plays  upon  the  charge  on  the  sole  of  A,  and  completes 
the  chemical  reaction  which  was  begun  in  B,  where  the 
charge  is  first  placed:  a  bridge-wall  separates  the  two.  The 
workman  judges,  by  the  appearance  and  consistency  of  a 

What  freezing  mixture  does  it  form  ?  510.  Give  the  formula  for  car- 
bonate of  soda.  How  was  it  procured  formerly  ?  Describe  Leblanc's  pro- 
cess ?  What  is  the  reaction  ?  Describe  fig.  354.  What  gas  is  formed  ? 
How  is  the  progress  of  the  operation  determined? 


SODIUM.  305 

portion  withdrawn  from  time  to  time,  of  the  progress  of  tho 
operation.  The  oxyd  of  carbon  forms  a  blue  flame  over  the 
surface,  which  disappears  when  the  reaction  is  over.  The 
heat  following  the  arrow,  next  plays  upon  solution  of  car- 
bonate of  soda  in  the  boiler  C,  the  lixivium  of  a  previous 
charge,  and  evaporates  it  to  dry  ness,  while  at  the  same 
time  the  more  dilute  solution  of  carbonate  is  heated  in  D, 
to  be  drawn  from  time  to  time  into  C.  The  steam  and  pro- 
ducts of  combustion  escape  by  the  chimney  0. 

Carbonate  of  soda  crystallizes  in  great  crystals  of  an  ob- 
lique form  and  containing  10  atoms  of  water,  viz.  NaO. 
C03-f  10HO,  equal  to  63  parts  water  in  100  of  the  salt. 
It  fuses  in  its  own  water  of  crystallization.  The  anhydrous 
carbonate,  as  it  comes  from  the  furnace,  is  called  soda-ash. 

Bicarbonate  of  soda  is  procured  by  exposing  soda-ash  to 
carbonic  acid  from  fermenting  grain,  as  in  distilleries,  or  by 
passing  this  acid  into  solution  of  carbonate.  It  is,  so  to 
speak,  a  carbonate  of  soda  plus  a  carbonate  of  water,  or 
NaO.C03-fHO.COa.  It  is  not  a  very  solute  salt :  100 
parts  of  water  take  up  8  of  bicarbonate.  Boiling  water 
expels  one  of  the  equivalents  of  carbonic  acid.  This  is 
the  salt  used  in  preparing  effervescent  draughts. 

The  sesquicarlonate  of  soda,  Trcma,  2Na0.3C02+4HO  is 
found  native  in  certain  lakes  in  Africa  and  South  America. 
It  crystallizes  in  right  rhomboidal  prisms,  unchanged  in  air, 
and  little  soluble  in  water.  / 

511.  Nitrate  of  Soda,  Soda  Saltpetre,  NaO.N05.— This 
salt  is  found  in  India  and  South  America,  where  extensive 
plains  are  covered  by  it,  as  at  Tarapaca  in  Chili,  and  Iquique 
in  Peru.  It  resembles  nitrate  of  potassa,  but  cannot  be  used 
to  replace  that  salt  in  gunpowder,  on  account  of  its  strong 
disposition  to  attract  water  from  the  air.  It  is  much  em- 
ployed, however,  in  procuring  nitric  acid,  and  also  as  a  fer- 
tilizer in  agriculture.  It  is  a  white  salt,  crystallizing  in 
rhombs,  specific  gravity  2-09,  very  soluable,  with  .a  cooling 
taste,  and  deflagrates  on  burning  coals  with  a  strong  yellow 
light.  By  carbonate  of  potassa  in  solution  it  is  immediately 
transformed  into  nitrate  of  potassa  and  carbonate  of  soda. 

How  is  the  solution  evaporated  ?  How  does  the  salt  crystallize  ?  How 
much  water  has  it?  How  is  the  bicarbonate  formed?  How  soluble  ? 
What  is  the  sesquicarbonate.  511.  What  is  the  history  of  nitrate  of  soda  ? 
What  does  it  resemble  ?  What  its  use  ?  How  does  it  act  with  com- 
bustibles ? 

20 


306  METALLIC   ELEMENTS. 

512  The  phosphates  of  soda  correspond  to  the  three  con< 
ditions  of  phosphoric  acid  (355)  before  noticed  :  they  are — • 

1.  Phosphate  of  Soda  (tribasic)  H0.2NaO.P05-f  24HO.— 
The  common  phosphate  of  soda  of  pharmacy  is  prepared  by 
precipitating  the  acid  phosphate  of  lime  (347)  with  a  slight 
excess   of  carbonate   of  soda.     It   crystallizes   in  oblique 
rhombic  prisms,  which  are  efflorescent.    The  crystals  dissolve 
in  four  parts  of  cold  water,  and  undergo  the  aqueous  fusion 
when  heated.     The  salt  has  a  pleasant  saline  taste,  and  is 
purgative;  its   solution  is  alkaline   to   test-paper.     When 
evaporated  above  90°  it  crystallizes  in  another  form,  with 
14  instead  of  24  atoms  of  water. 

2.  Subphosphate  of  soda  3NaO.P05-|-24HO  is  obtained 
by  adding  solution  of  caustic  soda  to  the  preceding  salt. 
The  crystals  are  slender  six-sided  prisms,  soluble  in  5  parts 
of  cold  water.     It  is  decomposed  by  acids,  even  the  carbonic, 
but  suffers  no  change  by  heat,  except  the  loss  of  its  water  of 
crystallization.    Its  solution  is  strongly  alkaline.     The  study 
of  these  salts  by  Prof.  Graham  has  greatly  enlarged  our 
views  of  chemical  philosophy. 

3.  Biphosphate'  of  Soda,  or  Superphosphate,  2HO.NaO. 
P05-j-HO. — This  salt  may  be  obtained   by  adding  phos- 
phoric acid  to  the  ordinary  phosphate,  until  it  ceases  to  pre- 
cipitate chlorid  of  barium,  and  exposing  the  concentrated 
solution  to  cold.     The  crystals  are  prismatic,  very  soluble, 
and  have  an  acid  reaction.     When  strongly  heated,  the  salt 
becomes  changed  into  monobasic  phosphate  of  soda. 

513.  Microcosmic  salt,  or  phosphate  of  soda  and  am- 
monia, (HO.NH4O.NaO.P05-|-8HO,)  is  much  used  in  blow- 
pipe operations  as  a  flux.     It  is  formed  by  dissolving  with  a 
gentle  heat,  1  part  of  chlorid  of  ammonium  and  6  or  7  parts 
of  phosphate  of  soda,  in  2  of  water.     Chlorid  of  sodium  is 
formed,  and  the  microcosmic  salt  crystallizes  out  in  rhombic 
prisms,  which  lose  8 HO  by  heat.     Its  fanciful  name  was 
derived  from  its  supposed  virtues  in  promoting  fertility  in 
the  impotent. 

514.  Bibasic  Phosphate  of  Soda,  Pyrophosphate  of  Soda, 
2NaO.P05-j-10HO. — Prepared   by  strongly  heating  com- 

512.  What  phosphates  are  named  ?  What  is  the  formula  of  the  tribasic  ? 
Give  its  properties.  What  is  the  subphosphate  ?  What  the  superphos- 
phate ?  What  of  Graham's  researches  ?  What  is  the  biphosphate  of 
eoda  ?  513.  What  is  microcosmic  salt  ?  How  formed  ?  514.  What  in 
bibasic  phosphate  ?  Give  its  formula. 


LITHIUM.  307 

mon  phosphate  of  soda,  dissolving  the  residue  in  water,  and 
recrystallizing.  The  crystals  are  very  brilliant,  permanent 
in  the  air,  and  less  soluble  than  the  original  phosphate  : 
their  solution  is  alkaline.  A  bibasic  phosphate,  containing 
an  equivalent  of  basic  water,  has  been  obtained ;  it  does  not, 
however,  crystallize. 

515.  Monobasic   Phosphate  of  Soda,  MetapliospJiate  of 
Soda,  NaO.P03. — Obtained  by  heating  either  the  acid  tri- 
basic phosphate,  or  microcosmic  salt.     It  is  a  transparent, 
glassy  substance,  fusible  at  a  dull  red-heat,  deliquescent, 
and  very  soluble  in  water.     It  refuses  to  crystallize,  and 
dries  up  in  a  gum-like  mass. 

The  tribasic  phosphates  give  a  bright  yellow  precipitate 
with  a  solution  of  nitrate  of  silver,  and  with  molybdate  of 
ammonia  :  the  bibasic  and  monobasic  phosphates  afford  white 
precipitates  with  the  same  substances.  The  salts  of  the  two 
latter  classes,  fused  with  excess  of  carbonate  of  soda,  yield 
the  tribasic  modification  of  the  acid. 

516.  Borax  ;  Bibomte  of  Soda;   Tincal ;  Na0.2B03+ 
10HO. — Borax   crystallizes   in   right   rhomboidal  prisms, 
which  are  soluble  in  15  or  16  parts  of  water  :  the  solution 
has  an  alkaline  reaction   and  sweetish  alkaline  taste.     It 
loses  its  water  by  heat,  and  being  very  fusible,  is  much  used 
as  a  flux  in  metallurgic  processes  and  as  a  blowpipe  reagent. 
It  is  entirely  procured  from  natural  sources  of  boracic  acid 
already  mentioned,  and  from  the  waters  of  several  lakes  iu 
Thibet,  in  which  it  is  dissolved. 


LITHIUM. 

Equivalent,  6-5.      Symbol,  L. 

517.  This  very  rare  metal  is  a  constituent  of  several 
minerals,  as  spodumene,  petalite,  lithia-inica  :  hence  its  name, 
from  lithos,  a  stone.  The  electrolysis  of  the  hydrate  afforded 
Davy  a  white  oxydizable  metal  analogous  to  sodium.  Ita 
small  atomic  weight  is  remarkable. 

The  oxyd  LO  is  an  alkali,  but  much  less   soluble   than 

515.  What  is  the  monobasic  phosphate  ?  What  are  the  tests  for 
tribasic  phosphates  ?  Of  the  bibasic  ?  How  are  the  bibasic,  &G.,  con- 
verted to  the  tribasic  form  ?  516.  What  is  borax  ?  What  its  source 
and  uses  ?  517.  What  is  lithium  ?  What  of  LO  ?  What  use  for  its  salts  ? 


308  METALLIC   ELEMENTS. 

potash  arid  soda.  Its  sulphate  is  a  beautiful  salt,  and  givea 
a  rosy  flame  to  alcohol.  The  lithia  compounds  all  give  this 
tint  to  the  outer  flame  of  the  blowpipe.  Some  of  its  salts 
ftave  been  used  internally  with  advantage  in  cases  of  urio 
*cid  calculus. 


AMMONIUM. 
Equivalent,  18.      Symbol,  NH4,  (hypothetical.') 

518.  Ammonium,  NH4. — The  compound  metallic  radical 
ol  ammonia  has  never  been  isolated,  although  we  have  reason 
to  laelieve  in  its  existence.  When  a  solution  of  ammonia,  or  of 
sal-ammoniac,  is  electrolyzed,  nitrogen  escapes  at  the  -\-  side 
_  4.  and  hydrogen  at  the  —  side,  fig.  355 ; 

but  if  the  latter  pole  is  made  by  using 
a  portion  of  mercury  in  the  bend  of  the 
tube  I,  no  hydrogen  is  evolved,  but 
the  mercury  swells  up,  loses  its  fluidity, 
becomes  like  soft  butter,  and  gradually 
Fig.  355.  attains  many  times  its  original  bulk, 

having  the  lustre  and  general  character  of  an  amalgam.  A 
more  simple  mode  of  forming  this  amalgam,  consists  in 
making  a  little  potassium  or  sodium  combine  by  heat  with 
about  100  times  its  weight  of  metallic  mercury.  This  alloy, 
when  placed  in  a  strong  solution  of  sal-ammoniac,  begins  at 
once  to  increase  in  volume  by  the  formation  of  the  ammo- 
niacal  amalgam,  until  it  has  attained  very  many  times  its 
original  bulk,  and  has  a  pasty,  butter-like  consistence. 

When  the  alloy  of  potassium  is  placed  in  hydrochloric  acid, 
the  alkaline  metal  decomposes  the  acid,  forming  chlorid 
of  potassium  and  evolving  hydrogen.  If  we  subsitute  for 
the  acid  (chlorid  of  hydrogen)  a  solution  of  chlorid  of  zino 
ZnCl,  a  like  decomposition  ensues ;  but  the  zinc,  instead  of 
being  set  free  like  the  hydrogen,  combines  with  mercury  to 
form  an  amalgam.  The  present  reaction  is  precisely  similar ; 
chlorid  of  ammonium  NH4C1  being  substituted  for  the 

518.  What  is  ammonium?  Give  its  history.  How  obtained  more 
simply  than  by  electrolysis  ?  What  is  the  appearance  of  the  amal- 
gam ?  What  illustration  is  given  from  the  alloy  in  HC1  and  in  ZnCl  ? 
What  is  the  reaction  in  the  present  case  ? 


COMPOUNDS   OF   AMMONIA.  309 

chlorid  of  zinc :  the  ammonium  which  is  liberated  com- 
bines with  the  mercury  and  forms  the  light  pasty  amalgam. 
It  crystallizes  in  cubes  at  32°,  whereas  pure  mercury  is  fluid 
even  at  a  temperature  of  — 39°  F.  It  is  evident  that  it  has 
combined  with  something  which  has  given  it  new  properties. 
This  is  supposed  to  be  the  metallic  radical  ammonium.  The 
spongy  mass,  as  soon  as  the  electric  action  ceases,  rapidly 
suffers  decomposition.  Ammonia  and  hydrogen  are  set  free 
in  the  proportion  of  1  to  2,  and  the  mercury  regains  its 
original  state,  unaltered.  Berzelius  and  other  able  chemists 
explain  this  reaction,  on  the  ground  that  the  ammonia,  by 
gaining  an  additional  equivalent  of  hydrogen,  assumes  the 
peculiar  character  of  a  metal,  and  unites  with  mercury, 
forming  an  amalgam.  This  hypothetical  metal  can  replace 
potassium  and  sodium  perfectly  in  combination,  and  is  there- 
fore isomorphous  with  them.  All  the  salts  of  ammonia  are, 
on  this  view,  derived  from  this  radical,  and  its  union  with 
the  second  class  gives  us  a  series  of  bodies  analogous  to  the 
chlorids,  bromids,  &c.,  of  the  other  electro-positive  bases. 


Compounds  of  Ammonium. 

519.  Chlorid  of  Ammonium  ;  Sal- Ammoniac,  NH4C1. — • 
This  salt  occurs  in  nature,  sometimes  quite  pure,  as  at  De- 
ception Island,  and  in  volcanic  districts  generally.  It  was 
originally  prepared,  in  Egypt,  (443,)  by  sublimation  from 
the  soot  of  the  burnt  camel's  dung.  This  is 
done  in  large  flasks  of  glass,  (fig.  356,)  the  sal- 
ammoniac  collects  in  the  upper  part,  and  the 
cake  is  removed  by  breaking  the  bottle.  It 
is  always  contaminated  by  organic  matters. 
It  is  also  obtained  largely  from  the  ammo- 
niacal  waters  of  the  gas-works.  It  is  purified 
by  evaporating  the  crude  solutions  to  dryness, 
after  treating  them  with  a  slight  excess  of 
chlorohydric  acid  to  neutralize  tha  free  am- 
monia, and  subliming  the  dry  mass  in  iron  Fi< 
vessels. 


What  is  the  product  of  its  decomposition  ?  What  is  the  explanation 
of  Berzelius?  How  are  the  ammoniacal  salts  viewed?  519.  What  if 
sal- ammoniac  ?  How  prepared  ? 


310 


METALLIC    ELEMENTS. 


It  has  a  sharp  saline  taste,  corrodes  metals  powerfully,  if 
soluble  in  three  parts  of  cold  water,  and  crystallizes  from  its 
solution  in  octahedrons.  The  sublimed  salt  has  a  fibrous 
texture,  and  is  very  tough  and  difficult  to  pulverize. 

The  formation  of  this  compound  is  easily  shown  by  using 
the  apparatus  already  figured,  (438,)  with  hydrochloric 
acid  in  one  flask  and  strong  ammonia  water  in  other ;  the 
commingling  of  the  dry  gases,  driven  over  by  heat  to  the 
central  bottle,  fills  it  with  a  white  cloud  of  sal-ammoniac, 
HCl-f  NH3  =  NH4C1.  The  preparation  and  properties  of 
ammonia  have  already  been  explained,  (444.) 

520.  Sulphydret  of  Ammonium,  (^Ilydrosulpliurct  of  Am- 
monia,} NH4S-{-HS. — This  very  useful  reagent  is  formed 
by  passing  a  long-continued,  slow  current  of  sulphuretted 
hydrogen  from  the  gas-bottle  a,  (fig.  357,)  through  the 
bottles  d,  €,/,  g,  filled  with  strong  water  of  ammonia.  This 

arrangement  is  a 
simple  form  of 
Woulfe's  appara- 
tus, (fig.  257.)  A 
single  bottle  of 
ammonia  (as  cT)  ia 
sufficient  for  all 
common  pur- 
poses. It  should 
be  kept  cold.  The 
ammonia  absorbs 


Fig.  357. 


an  enormous  quan- 
tity of  the  gas,  and 
the  resulting  sulphuret,  which  has  the  strong  odor  of  the 
gas,  is  colorless  at  first,  but  gradually  assumes  a  yellow 
color.  It  forms  numerous  salts  with  electro-negative  sul- 
phurets,  being  itself  a  powerful  sulphur  base.  It  is  an 
invaluable  reagent  as  a  precipitant  of  the  metals,  and  is  also 
used  in  medicine. 

There  are  several  simple  sulphurets  of  ammonium,  but  they 
are  of  no  particular  interest. 

521.   Sulphate  of  Ammonia,  or  Sulphate  of  Oxyd  of 


What  its  properties  ?  How  formed  artificially  ?  520.  What  is  sulphydret 
of  ammonium  ?  Describe  fig.  357.  What  is  the  chemical  character  of  this 
body  ?  What  its  uses  ? 


COMPOUNDS  OP  AMMONIA.  311 

Ammonium ,  NH4O.S03-|-HO. — This  salt,  which  is  a  pow- 
erful fertilizer,  is  procured  in  the  large  way  by  neutralizing 
the  ammoniacal  liquor  of  the  gas-works  by  sulphuric  acid  : 
or  it  may  be  easily  obtained  pure  by  neutralizing  dilute  sul- 
phuric acid  with  carbonate  of  ammonia. 

522.  There  are  several  carbonates  of  ammonia.      The 
common  sal-volatile  of  the  shops,  with  a  pungent  smell  and 
alkaline  reaction,  is  nearly  a  sesquicarbonate  2NH40.3COa. 
Exposed  to  the  air,  this  salt  becomes  a  white  inodorous 
powder,  which  is  the  bicarbonate.     The  sesquicarbonate  is 
a  very  valuable  salt  to  the  chemist.     It  forms  the  basis  of 
the  smelling-bottles  so  much  in  use.    The  dry  white  powder 
formed  by  the  contact  of  dry  carbonic  acid  and  ammonia 
in  an  apparatus  like  figure  319,  is  a  neutral  anhydrous 
carbonate  NH3.C03,  very  pungent  and  volatile,  dissolving 
readily  in  water. 

523.  Nitrate  of  Ammonia,  or  Nitrate  of  Oxyd  of  Am 
monium,  NH4O.N05-]-HO. — This   salt  has  already  been 
noticed  (338)  under  the  description  of  nitrous  oxyd.     Its 
crystals  resemble  nitre,  deliquesce  in  moist  air,  and  dissolve 
in  2  parts  of  cold  water,  the  solution  sinking  the  thermo- 
meter to  zero,  (124.)     It  deflagrates  on  burning  coals  like 
nitre,  and  hence  received  the  old  name  of  nitrum  flammens . 

524.  All  the  ammoniacal  salts  are  volatilized  by  a  high 
temperature,  and  yield  the  ammoniacal  odor  by  trituration 
with  caustic  potassa  or  lime,  or  by  boiling  with  solutions  of 
potash.    They  are  all  soluble,  and  give  a  sparingly  soluble, 
yellow,  crystalline  precipitate  with  chlorid  of  platinum. 

521.  What  is  sulphate  of  ammonia  ?  522.  What  carbonates  are  named  ? 
What  one  is  formed,  from  the  union  of  the  gases  ?  523.  What  is  nitrate 
of  ammonia?  Give  its  formula.  How  decomposed  by  heat?  What  id 
its  frigorific  pow»r  ?  What  name  had  it  ?  524.  What  are  tests  for  am- 
moniacal salts " 


312  METALLIC  ELEMENTS. 


CLASS  II.  METALS  OF  THE  ALKALINE  EARTHS. 

525.  This  class  includes  barium,  strontium,  calcium,  and 
magnesium,  the  bases  of  the  alkaline  earths,  baryta,  strontia, 
lime,  and  magnesia :  these  are  all  soluble  to  some  extent  in 
water,  with  an  alkaline  reaction,  but  differ  very  much  in  the 
eolubility  and  other  properties  of  their  various  salts. 


BARIUM. 

Equivalent  68-5.      Symbol,  Ba. 

526.  Barium  is  a  silver-white  malleable  metal,   easily 
oxydized,  and  melts  at  a  red  heat.     It  was  procured  by 
Davy  by  a  process  similar  to  that  which  yielded  potassium, 
&c.    It  is  better  obtained  by  passing  vapor  of  potassium  over 
baryta  (oxyd  of  barium)  heated  to  redness  in  an  iron  tube. 
Mercury  dissolves  out  the  reduced  metal,  and  the  amalgam 
is  then  distilled.     It  is  named,  from  the  striking  weight  of 
its  salts,  from  bar  us,  heavy. 

527.  Baryta,  or  Protoxyd  of  Barium,  BaO. — Baryta  is 
best  obtained  by  decomposing  the  nitrate  at  a  red  heat.     It 
is  a  dry,  gray  powder,  which  combines  with  water  to  form  a 
hydrate,  slaking  with  the  evolution  of  great  heat  and  even 
light.     Its  density  is  545.     The  hydrate  dissolves  in  two 
parts  of  hot  water,  or  twenty  of  cold,  and  crystallizes  in  flat 
tables.     The  aqueous  solution  is  a  valuable  test  for  carbonic 
acid. 

Sulphate  of  baryta,  or  heavy  spar,  is  found  abundantly,  as 
an  associate  of  other  minerals,  in  veins ;  and  from  it,  or  the 
native  carbonate  of  baryta,  ail  the  artificial  compounds  of 
barium  are  formed. 

528.  The  peroxyd  of  barium  BaO.,  is  formed  by  pass- 
ing pure  oxygen  gas  over  the  oxyd  heated  to  dull  redness  in 
a  porcelain  tube.    It  is  chiefly  interesting  as  being  the  means 
of  procuring  the  peroxyd  of  hydrogen,  (420.) 

525.  What  are  the  metals  of  the  alkaline  earths  ?  526.  What  is  the  equi- 
valent of  barium?  Give  its  properties.  Whence  its  name?  527.  What 
is  baryta?  How  docs  it  act  with  Avater?  What  its  density?  528.  How 
is  peroxyd  of  barium  formed,  and  for  what  used  ? 


STRONTIUM.  313 

Chlorid  of  Barium,  BaCl  +  2HO.—  This  salt  occurs  in 
white  tabular  crystals,  containing  two  equivalents  of  water, 
which  are  expelled  by  heat.  It  dissolves  in  a  little  more 
than  twice  its  weight  of  cold  water,  and  the  solution  is  a 
valuable  reagent  for  detecting  the  presence  of  sulphuric  acid. 

529.  The  nitrate  of  baryta  BaO.N05-fHO  is  also  a  soluble 
white  salt,  which  crystallizes  in  anhydrous  octahedrons,  and 
dissolves  in  eight  parts  of  cold  or  three  parts  of  hot  water. 
Both  it  and  the  chlorid  are  prepared  by  dissolving  the  native 
or  artificial  carbonate  in  the  proper  acid. 

Sulphate  of  baryta,  heavy  spar,  BaO.S03,  is  a  mineral 
found  abundantly  in  many  places  in  this  country,  as  at 
Cheshire,  Connecticut.  It  crystallizes  in  tabular  modifica- 
tions of  the  rhombic  prism,  often  very  beautiful.  It  is  also 
found  massive  at  Pillar  Point,  New  York.  Its  specific  gra- 
vity (4-3  to  4-7)  gives  it  the  name  of  heavy  spar.  It  is  quite 
insoluble  in  water  or  acids,  and  not  easily  decomposed.  When 
strongly  heated  with  charcoal  powder,  however,  it  suffers 
decomposition,  BaO.S03  -f  4C  =  BaS  -f  4CO ;  carbonic 
oxyd  is  given  off,  and  the  soluble  sulphuret  of  barium  may 
be  dissolved  out  from  the  coaly  mass. 

Sulphate  of  baryta  is  extensively  ground  up  for  a  pigment, 
being  mixed  with  white-lead  as  an  adulteration. 

530.  Carbonate  of  Baryta ,  BaO.C03,  or  the  wither ite  of 
mineralogists,  is  a  mineral  of  some  interest,  and  useful  as 
the  chief  source  of  the  various  compounds  of  baryta.     All 
the  soluble  baryta  salts  are  poisonous,  and  their  presence 
may  always  be  detected  by  sulphuric  acid,  or  a  soluble  sul- 
phate, with  which  they  form  the  insoluble  sulphate  of  baryta. 

The  compounds  of  barium  give  a  peculiar  yellow  color  to 
the  flame  of  the  blowpipe,  different  from  the  yellow  flame 
of  soda. 

STRONTIUM. 
Equivalent,  44.      Symbol,  Sr. 

531.  Strontium  is  obtained  from  its  oxyd  in  the  same 
manner  as  barium,  and,  like  it,  is  a  white  metal,  oxydized 

Give  the  characters  of  the  chlorid  of  barium.  For  what  is  it  a  test? 
529.  How  is  the  nitrate  of  baryta  characterized?  How  is  heavy  spaf 
found  in  nature  ?  Give  its  formula  and  properties.  530.  What  is  car- 
bonate of  baryta  ?  What  character  have  the  soluble  salts  of  baryta  ?  How 
is  their  presence  detected  ?  531.  How  is  strontium  obtained,  and  how 
characterized  ? 


314  METALLIC   ELEMENTS. 

easily  in  the  air,  and  decomposing  water  at  common  tempera- 
tures. There  are  two  oxyds,  the  protoxyd  and  the  peroxyd 
of  strontium,  similar  in  properties  to  the  like  oxyds  of  barium. 
The  sulphate  of  strontia  (celestine)  is  a  rather  abundant 
mineral,  and  the  carbonate  (strontia  nite)  is  much  esteemed 
by  mineralogists.  They  are  very  similar  in  properties  to 
the  sulphate  and  carbonate  of  baryta. 

532.  The  chlorid  of  strontium  SrCl  -f  OHO  is  a  deli- 
quescent  salt,  soluble  in  two  parts  of  cold  water.     It  loses 
its  water  of  crystallization  by  heat.     Both  it  and  the  nitrate 
of  strontia  SrO.N05  are  much  employed  by  pyrotechnists 
in  forming  the  red  fire  of  theatres  and  fireworks.      All  the 
compounds  of  strontium  give  a  peculiar  red  tint  to  the  flame 
of  the  blowpipe,  while  the  barytic  salts  do  not.      The  salts 
of  strontia  are  not  poisonous. 

CALCIUM. 

Equivalent,  20.      Symbol,  Ca. 

533.  Calcium  is  a  yellowish-white  metal,  obtained  like 
barium,  and  has  so  strong  a  disposition  to  combine  with 
oxygen  that  it  is  difficult  to  observe  its  properties. 

534.  Protoxyd  of  Calcium,  Lime,  CaO. — This  most  valu- 
able substance,  so  well  known  as  quicklime,  is  procured  in 
a  state  of  great  purity  by  heating  the  stalactites  from  caverns, 
or  the  purest  statuary  marble,  for  some  hours  to  full  redness 
in  an  open  crucible.     The  carbonic  acid  and  organic  coloring 
matter  are  driven  off,  and  oxyd  of  calcium  (lime)  nearly  pure 
remains.     Pure  lime  is  a  white,  very  infusible,  and  rather 

hard  body,  having  a  density  of  3-18.  It 
has  a  great  affinity  for  carbonic  acid,  taking 
it  from  the  air  and  falling  to  powder,  (air- 
slaking.)  It  also  combines  with  water  to 
form  a  hydrate,  evolving  great  heat,  (slak- 
ing.) When  this  operation  is  performed 
under  a  glass  bell,  (fig.  358,)  the  vapor  of 
water  at  first  condensed  on  the  walls  of 
_____  the  jar  soon  forms  a  transparent  atmosphere 
>  358.  of  steam,  which,  when  the  bell  is  raised, 

What  familiar  salts  of  this  ratal  are  found  native  ?  532.  Describe  the 
chlorid  of  strontium.  What  is  it  used  for?  533.  What  is  calcium,  and 
how  is  it  obtained  ?  Give  its  equivalent?  534.  What  is  lime?  How 
procured?  What  its  density  ?  What  is  air-slaking?  What  slaking  by 
water  ? 


CALCIUM.  315 

breaks  on  the  air  in  a  dense  cloud  of  vapor.  The  heat  is 
greatest  when  the  water  is  about  half  the  weight  of  lime 
employed.  Is  sufficiently  high  often  to  inflame  gunpow- 
der. The  hydrate  CaO.HO  is  a  dry,  bulky  powder,  soluble 
in  1000  parts  of  water,  to  form  lime-water.  With  water 
it  forms  a  milk  of  lime;  a  corrosive  paste  used  to  re- 
move hair  from  hides.  Lime-water  is  a  valuable  reagent 
and  antacid ;  it  has  a  disagreeable  alkaline  taste ;  blues 
reddened  litmus,  and  absorbs  carbonic  acid  from  the  air,  by 
which  it  becomes  milky  from  precipitation  of  carbonate  of 
lime  soluble  in  excess  of  carbonic  acid. 

535.  Common  lime  is  prepared  by  heating  limestone  (car- 
bonate of  lime)  in  large  stone  furnaces,  filled  from  the  top 
with  the  limestone  and  fuel ;  the  fire  is  kept  up  constantly, 
by  renewed  charges  of  the  materials  at  top,  while  the  pre- 
pared caustic  lime  is  drawn  out  at  the  bottom.    The  carbonic 
acid  is  much  more  rapidly  expelled  when  the  vapor  of  water 
and  other  products  of  combustion  come  in  contact  with  the 
heated  limestone.    Indeed,  it  is  hardly  possible  by  heat  alone 
in  close  vessels  to  expel  the  C03,  since  carbonate  of  lime  is 
fusible  under  those  circumstances  without  decomposition. 

Mortar  acts  as  a  cement  by  the  slow  formation  of  carbon- 
ate of  lime,  which  binds  together  the  grains  of  sand  that 
.make  up  the  greater  part  of  the  mixture.  The  smaller  the 
portion  of  lime  used,  and  the  sharper  the  silicious  sand 
employed,  the  more  firm  will  be  the  cement  at  last;  but  it 
is  then  so  much  more  difficult  to  work,  that  an  excess  of 
lime  is  usually  employed.  The  presence  of  oxyd  of  iron 
and  manganese,  of  alumina,  magnesin,  silica,  and  other  like 
substances  in  a  limestone,  gives  the  lime  prepared  from  it 
the  property  of  hardening  under  water,  when  it  is  called 
hydraulic  lime. 

Lime  is  much  used  in  improved  agriculture,  as  a  manure. 
It  acts  to  decompose  vegetable  matters,  to  neutralize  acids, 
dissolve  silica,  and* retain  carbonic  acid.  It  is  always  present 
naturally  in  every  fertile  soil,  and  is  a  constant  ingredient  in 
the  ashes  of  most  plants. 

536.  Clilorid  of  Calcium,  CaCl. — The  solution  of  lime, 


What  heat  is  given  out  in  this  operation  ?  Where  greatest  ?  How 
soluble  is  the  hydrate  ?  535.  How  is  common  lime  prepared  ?  Why  is 
vapor  of  water  useful  in  the  process  ?  How  does  mortar  act  as  a  cement? 
What  is  hydraulic  lime  ?  536.  What  is  the  chlorid  of  calcium  ? 


816 


METALLIC   ELEMENTS. 


or  of  its  carbonate,  in  hydrochloric  acid  to  saturation,  gives 
us  this  chlorid.  It  is  when  fused  a  white  crystalline  solid, 
with  a  great  avidity  for  moisture,  and  for  this  reason  it  is 
used  in  the  desiccation  of  gases,  &c.  It  is  soluble  in  alcohol, 
with  which  it  forms  a  definite  crystallizable  compound.  It 
forms  a  powerful  freezing  mixture  with  ice,  (124.) 

The  sulphurets  and  phosphurets  of  calcium  have  little  in- 
terest. The  phosphuret  being  decomposed  by  water,  is  an 
available  source  of  the  spontaneously  inflammable  phosphu- 
retted  hydrogen,  (fig.  326.) 

537.  Sulphate  of  Lime — Gypsum — Selenite,  CaO.S03* 
—This  salt,  in  the  form  of  hydrate  CaO.S03-f  2HO,  is 
abundant  in  nature,  and  is  much  used  in  agriculture  as  a 
manure,  being  ground  to  powder;  and,  after  expelling  the 
water  by  heat,  as  a  material  for  stucco  and  plaster  casts. 
It  is  then  commonly  known  as  "  plaster  of  Paris."  The  varie- 
gated and  fine  white  varieties  are  called  alabaster.  When 
crystallized  in  transparent  flexible  plates,  it  is  called  selenite. 
These  crystals  are  sometimes  compound  in 
such  a  manner  as  to  present  an  arrow-head 
form,  like  fig.  359.  Such  crystals  are  called 
hemitropes.  Anhydrous  gypsum  CaO.S03  also 
is  found  native,  and  is  known  by  the  minera- 
logical  name  of  anhydrite. 

Gypsum  is  frequently  associated  with  rock- 
salt.  It  is  soluble  in  about  500  parts  of  water, 
and  is  present  in  most  natural  waters.  By 
a  heat  of  250°  to  270°  it  loses  its  water  of 
composition:  when  the  anhydrous  powder  is 
moistened,  the  lost  water  is  regained,  and  it 
becomes  solid ;  but  if  heated,  even  to  330°,  it 
no  longer  regains  its  water  of  composition.  It 
fuses  at  a  red  heat  to  a  crystalline  anhydrous  mass.  This 
power  of  resolidification,  when  mixed  with  water,  gives 
gypsum  its  value  in  copying  works  of  art,  and  in  forming 
stucco  ornaments.  By  using  solution  of  common  alum  in 
place  of  water,  gypsum  becomes  very  hard,  and  is  thus 
treated  for  producing  pavements. 


Fig.  359. 


For  what  is  it  used  ?  What  is  the  phosphuret  of  calcium  used  for? 
537.  Give  the  common  names  of  sulphate  of  lime.  For  what  is  it  used  ? 
Give  its  properties.  What  is  fig.  359  ?  How  is  gypsum  hardened  ?  On 
what  docs  its  use  in  stucco  depend  ?  What  is  anhydrite  ? 


CALCIUM.  317 

538.  Fluorid  of  Calcium,  Fluor-spar,  CaF. — This  is  a 
rather  abundant  mineral,  being  found  beautifully  crystallized, 
of  various  colors,  in  the  cube  and  its  modifications.     It  is  the 
principal  source  from  which  we  obtain  the  fluohydric  acid 
(433)  by  decomposition  with  sulphuric  acid.     It  often  phos- 
phoresces  very  beautifully  with   heat,  emitting   a    green, 
yellow,  or  purple  light,  at  a  temperature  below  redness. 

539.  Phosphates  of  Lime. — There  are  several  phosphates 
of  lime  corresponding  to  the  several  phosphoric  acids,  (355.) 
The  earth  of  bones  is  a  tribasic  phosphate  of  lime,  and  the 
mineral  known  as  apatite  is  also  a  phosphate  of  lime.     The 
phosphates  of  lime  are  insoluble  in  water,  but  dissolve  in 
dilute  acids.     All  cereal  grains,  and  many  other  vegetables, 
contain  phosphate  of  lime  in  their  ashes,  and  this  salt  is 
therefore  an  indispensable  ingredient  of  all  fertile  soils,  and 
the  form  in  which  phosphorus  is  introduced  into  the  animal 
structure. 

540.  Carbonate   of   Lime — Marble — Calcareous    Spar, 
CaO.C03. — This  is  one  of  the  most  abundant  minerals  of 
the  earth,  forming  in  limestone  vast  mountains  and  wide- 
spread geological  deposites.     It  oc- 
curs most  superbly  crystallized  in 

rhombohedral  forms,  which  consti- 
tute brilliant  ornaments  in  mineralo- 
gical  collections.  The  transparent 
double  refracting  Iceland  spar,  (fig. 
360,)  and  the  dimorphous  form, 
arragonite,  are  examples  of  this  salt.  Fig.  360. 

It  is  soluble  in  dilute  acids,  with  escape  of  carbonic  acid,  and 
is  also  decomposed  by  heat,  leaving  quicklime. 

Water  aided  by  carbonic  acid,  and  perhaps  by  the  organic 
acids  of  the  soil  also,  dissolves  carbonate  of  lime,  and  again 
deposits  it  in  stalactites  and  stalagmites,  on  exposure  to  the 
air.  These  phenomena  are  beautifully  seen  in  Mammoth 
Cave,  Schoharie  Cave,  and  many  similar  situations.  The 
stalactites  depend  from  the  roof,  growing  by  the  deposit  of 
freshly  precipitated  portions  of  carbonate  of  lime  on  their 

538.  What  is  fluor-spar  ?  How  is  it  found  ?  For  what  used  ?  What 
beautiful  property  has  it  ?  539.  What  phosphates  of  lime  are  known  ? 
In  what  do  we  find  phosphate  of  lime  ?  How  does  phosphorus  enter  tho 
system  ?  540.  What  is  the  formula  of  carbonate  of  lime  ?  What  other 
names  has  it  ?  What  is  formed  from  it  ?  What  optical  property  has  it? 
How  does  water  dissolve  it  ?  What  are  stalactites  and  stalagmites  ? 


METALLIC   ELEMENTS. 


surfaces,  which  are  kept  moist  by  the  trickling  of  water  con- 
taining the  salt  in  solution.  The  water  which  falls  to  the 
floor  from  the  point  of  each  stalactite  slowly  builds  up  a  coni- 
cal mass  called  a  stalagmite,  and  when  these  meet  they  form 
a  column.  All  these  stages  are  well  shown  in  fig.  361, 


Fig.  3d. 

from  Regnault.  Before  these  fairy-like  creations  of  nature's 
architecture  are  darkened  by  torches,  their  beauty  is  en- 
chanting. 

541.  Hypochlorite  of  Lime,  CaO.CIO,  Bleaching- Pow- 
der.— This  valuable  compound  is  formed  when  chlorine  gas 
is  gradually  admitted  to  hydrate  of  lime  slightly  moist  and 
kept  cool.  The  chlorine  is  absorbed  largely,  and  the  Ueuch- 
ing-powder  of  the  arts  is  formed.  Bleaching- powders  con- 
tain a  mixture  of  hypochlorite  of  lime,  chlorid  of  calcium, 
and  hydrate  of  lime.  It  is  a  soft  white  powder,  easily  soluble 
in  about  10  parts  of  water,  giving  a  highly  alkaline  solution, 
which  bleaches  feebly.  It  is  employed  by  dipping  the 
goods  in  the  weak  solution,  and  then  in  very  dilute  acid 
water.  The  chlorine  is  thus  evolved  and  does  its  work. 
Several  repetitions  are  needed  to  complete  the  process,  and 
the  acid  is  washed  out  with  care.  This  compound  emits  a 
strong  smell,  which  is  similar  to  chlorine,  but  is  due  t& 


Describe  their  formation  as  in  fig.  361.     What  is  bleachLng-powder  ? 
How  formed  ?    How  employed  ? 


MAGNESIUM.  3 19 

hypochlorous  acid ;  it  is  very  useful  for  disinfecting  offen- 
sive apartments,  and  its  energy  is  increased  by  the  addition 
of  a  little 'acid  water.  The  disinfecting  liquid  of  Labarraque 
is  a  compound  of  chlorine  with  soda,  similar  in  composition 
to  solution  of  bleaching-powder. 

The  best  bleaching-powders  contain  39  parts  of  available 
chlorine,  and  2  parts,  in  combination,  as  chlorid  of  calcium. 
If  one  equivalent  of  each  ingredient  were  present  they 
would  be  in  the  proportion  of  48 -57  chlorine  and  5143  parts 
hydrate  of  lime.  Ordinary  bleaching-powders  contain  only 
about  30  per  cent,  of  chlorine.  The  mode  of  determining 
the  amount  of  chlorine  present  is  called  chlorimetry,  and 
is  based  on  the  quantity  of  sulphate  of  indigo  which  is 
decolorized  by  a  standard  solution  of  chlorine.  The  salts 
of  lime  are  not  precipitated  by  ammonia,  but  form  an  entirely 
insoluble  oxalate,  with  oxalic  acid  or  oxalate  of  ammonia. 


MAGNESIUM. 

Equivalent,  12 -2.     Symbolj  Mg. 

542.  Magnesium  is  obtained  by  decomposing  the  chlorid 
of  that  metal  heated  to  redness  in  a  glass  tube,  by  passing 
over  it  the  vapor  of  potassium  or  sodium.     Chlorid  of  po- 
tassium or  sodium  is  formed,  and  the  metallic  magnesium 
is  separated  by  dissolving  out  the  soluble  chlorid. 

It  is  a  white  metal,  malleable  and  brilliant.  It  fuses 
with  a  red  heat,  and  if  heated  to  redness  in  the  air,  burns 
with  a  brilliant  light,  producing  oxyd  of  magnesium.  It 
does  not  tarnish  in  dry  air,  and  does  not  decompose  water 
even  at  212°,  but  dissolves  in  acids  with  escape  of  hydrogen. 

543.  Oxyd   of  Magnesium,   Calcined  Magnesia ,  MgO. 
This  substance  is  left  when  the  carbonate  of  magnesia  is 
heated  to  redness/    It  is  a  white,  very  light,  earthy  powder, 
insoluble  in  water,  but  readily  soluble  in  weak  acids.     It 
occurs  in  nature  crystallized  in  regular  octahedrons,  form- 
ing the  mineral  periclase.     It  is  much  used  in  medicine  as 
a  mild  and  efficient  aperient.      The  hydrate  of  magnesia 

"What  is  Labarraque's  liquor  ?  What  is  the  composition  of  bleaching- 
powder  ?  What  is  chloriinetry  ?  What  precipitates  the  salts  of  lime  ? 
542.  Give  the  equivalent  and  preparation  of  magnesium.  What  are  its 

Soperties?     543.  What  is  the  oxyd  of  magnesium?     How  is  it  used? 
Dvr  found  in  nature  ? 


320  METALLIC   ELEMENTS. 

MgO.HO  is  formed  wnen  magnesia  is  precipitated  from  its 
solutions  by  an  alkali.  Heat  expels  the  equivalent  of  water, 
leaving  calcined  magnesia.  Tho  hydrate  is  found  beau- 
tifully crystallized  in  thin  pearly  plates  at  Hoboken,  New 
Jersey. 

544.  Chlorid  of  Magnesium,  MgCl. — This  chlorid  is  best 
prepared  by  neutralizing  equal  portions  of  chlorohydric  acid, 
ona  with  magnesia  and  the  other  with  ammonia,  mixing  the 
two  portions  and  evaporating  to  dryness.      The  dry  mass  is 
heated  in  a  covered  crucible  as  long  as  sal-ammoniac  is  given 
off,  when  pure  chlorid  of  magnesium  is  left.  It  is  a  very  deli- 
quescent salt,  and  supplies  the  means  of  procuring  metallic 
magnesium.     When  magnesia  is  dissolved  in  hydrochloric 
acid,  a  hydrated  chlorid  of  magnesium  results.    By  heat  the 
water  is  expelled,  carrying  with  it  chlorohydric  acid,  and 
leaving  pure  magnesia  behind.     The  bittern  of  salt  springs 
is  chlorid  of  magnesium ;  it  exists  in  sea-water,  and  is  the 
largest  ingredient  in  the  waters  of  the  Dead  Sea.    The  iodid 
and  bromid  of  magnesium  are  also  soluble  salts,  but  the 
fluorid  is  insoluble. 

545.  Sulphate  of  Magnesia,  Epsom   Salts,  MgO.SO?-f- 
7HO. — This  well-known  salt  is  easily  formed  by  dissolving 
magnesia,  or  its  carbonate,  in  sulphuric  acid.     It  is  also 
found  native  at  Corydon,  Illinois.     In  the  waters  of  Epsom 
Spa,  in  England,  and  in  numerous  mineral  waters,  it  is  a 
large  constituent.    It  is  made  on  a  large  scale  by  dissolving 
serpentine  rock  in  strong  sulphuric  acid.    It  is  very  soluble, 
and,  like  all  the  soluble  salts  of  magnesia,  has  a  peculiar 
bitter  taste. 

546.  The  carbonate  of  magnesia,  magnesite,  MgO.COa/ 
is  found  native  in  magnesian  rocks,  and  is  formed  artificially 
by  decomposing  any  of  the  soluble  salts  of  magnesia  by  an 
alkaline  carbonate,  giving  the  magnesia  alba  of  pharmacy. 
It  is  insoluble  in  water;   but  a  solution  of  carbonic  acid 
dissolves  it,  and  forms  the  celebrated  Murray's  solution  of 
magnesia.     It  is  decomposed  by  contact  of  air,  carbonic  acid 
escapes,  and  carbonate  of  magnesia  is  thrown  down.     The 
double  carbonate  of  magnesia  and  lime  is  found  as  an  ex- 

What  is  calcined  magnesia?  544.  How  is  the  chlorid  of  magnesium 
prepared?  Describe  it.  When  magnesia  is  dissolved  in  chlorohydric 
acid,  what  happens  ?  545.  What  is  the  composition  of  sulphate  of  mag- 
nesia? How  is  it  made  in  the  large  way  ?  In  what  waters  is  it  found? 
646.  What  is  carbonate  of  magnesia?  What  is  Murray's  solution? 


ALUMINUM.  321 

tensive  rock  formation,  called  dolomite,  and  when  crystal 
lized,  pearl  spar. 

Phosphate  of  soda  with  ammonia  throws  down  a  crys 
talline  insoluble  salt  from  magnesian  solutions,  which  is 
the  double  phosphate  of  magnesia  and  ammonia.  This  is 
the  most  ready  mode  of  testing  for  the  presence  of  magnesia. 

547.  Magnesia   occurs  abundantly  in  nature   as  a  con- 
stituent of  many  minerals,  as  well  as  in  the  form  of  hydrate 
and  carbonate.     The  silicates  of  magnesia  form  a  very  im- 
portant class  of  minerals,  of  which  talc,  soap-stone,  pyroxene, 
hornblende,  serpentine,  &c.,  are  examples.     Magnesia  is  also 
found  in  the  ashes  of  most  plants,  in  union  with  phosphorio 
acid. 

CLASS  III.— METALS  OF  THE  EARTHS. 

ALUMINUM.     Al.  —  13-69. 

548.  Aluminum  is  best  obtained,  like  magnesium,  by  the 
action  of  sodium  or  potassium  on  its  chlorid.      It  is  a  gray 
powder,  not  easily  melted,  has  a  metallic  lustre,  and  burns, 
when  heated  in  the  air,  with  a  bright  light,  forming  alumina. 

549.  Alumina;   Sesquioxyd  of  Aluminum  ;    Corundum, 
A1203. — Pure  alumina  is  found  crystallized  in  those  precious 
gems,  the  oriental  ruby  and  sapphire,  which  are  next  in 
hardness  and  value  to  the  diamond.     Emery  (cornudum)  ig 
also  nearly  pure  alumina.     Alumina  is  an  abundant  ingre- 
dient in  many  other  minerals,  and  forms  a  large  part  of  many 
slaty  rocks,  from  whose  decomposition  clays  are  produced. 

Pure  alumina  is  a  fine  white  powder,  not  rough  and  gritty 
like  silica.  Its  density  is  4-154.  It  is  infusible  except 
under  the  oxyhydrogen  blowpipe.  After  ignition  it  is  al- 
most or  entirely  insoluble. 

Hydrate  of  alumina  Al203-f-3HO  exists  in  the  minerals 
diaspore  and  gibbsiie.  Alumina  is  precipitated  as  a  hydrate 
from  solution,  by  either  potash,  soda,  or  ammonia,  and  their 
carbonates;  an  excess  of  the  first  two  will  redissolve  the 
precipitate.  The  hydrate  is  very  bulky,  and  shrinks  very 


What  test  have  we  for  magnesia  ?  547.  How  does  magnesia  occur  in 
uature  ?  Mention  some  of  its  silicates.  548.  How  is  aluminum  obtained? 
What  are  its  properties  and  density?  549.  What  is  the  formula  of  alu- 
mina ?  In  what  is  it  found  pure  ?  How  arc  the  hydrous  and  anhydroua 
alumina  distinguished?  What  precipitates  and  Avhat  redissolves  it? 


* 

322  METALLIC   ELEMENTS. 

much  on  drying.  Hydrosulphuret  of  ammonium  throws 
down  alumina.  The  anhydrous  alumina  is  almost  insoluble 
in  acids,  while  the  hydrate  is  readily  dissolved,  forming  salts 
of  a  peculiar  astringent  taste,  familiarly  known  in  common 
alum. 

The  chlorid  of  aluminum  has  no  particular  interest  except 
as  a  means  of  procuring  the  metal. 

Aluminate  of  potassa  KO.  A1303  is  formed  when  a  solution 
of  alumina  in  potassa  is  gently  evaporated  :  it  appears  in 
crystalline  grains.  IJaryta  an(^  magnesia  afford  similar 
examples.  Spinel,  a  mineral  species,  is  an  aluminate  of 
magnesia  MgO.Al303.  These  are  instances  of  the  double 
function  which  alumina  possesses  of  acting  the  part  both  of 
acid  and  base,  (474,  3.) 

550.  Sulphate  of  Alumina,  A1303.3S03+1SHO.—  This 
salt  is  prepared  by  saturating  dilute  sulphuric  acid  with 
alumina :  it  has  a  sweetish  astringent  taste,  is  soluble  in  2 
parts  of  water,  and  crystallizes  in  thin  plates. 

Alums. — Sulphate  of  alumina  forms,  with  potash.,  soda, 
and  ammonia,  double  salts  of  much  interest,  called  alums. 
They  are  all  soluble  salts,  with  a  sweetish  astringent  taste, 
and  crystallize  in  the  regular  system,  or  first  class,  (44,) 
usually  as  modified  octahedrons,  which  have  uniformly  24 
equivalents  of  water  of  crystallization.  Common  potash- 
alum  has  the  formula  Ala03.3S03+KO.S03+24HO,  (256;) 
it  dissolves  in  18  parts  of  cold  water,  and  the  solution  has 
an  acid  reaction.  The  water  of  crystallization  of  the  alums 
is  expelled  by  heat :  the  salt  first  suffers  watery 
fusion,  and  then  swells  up  into  a  light  porous 
mass,  many  times  the  volume  of  the  salt  em- 
ployed, and  protruding  beyond  the  vessel 
employed,  as  in  fig.  362.  This  is  called  burnt- 
alum.  All  the  basic  sesquioxyds  isomorphous 
with  alumina  may  replace  it  in  the  constitu- 
tion of  an  alum. 

Alum  and  acetate  of  alumina  are  largely 
employed  in  the  arts  of  dyeing  and  tanning. 
Fig.  362.       Alumina  combines  with  coloring  matters,  and 
seems  to  form  a  bond  of  union  between  the  fibre  of  the  cloth 


What  salts  does  it  form?  What  is  aluminate  of  potassa?  What  ij 
spinel?  Give  the  formula  of  alum.  550.  What  is  burnt  alum?  What 
is  the  use  of  alums  ? 


ALUMINUM,  o23 

and  the  color.  In  this  it  is  said  to  act  the  part  of  a  mor- 
dant. When  alum  is  added  to  the  solution  of  a  coloring 
matter,  and  the  alumina  is  then  precipitated  with  an  alkali, 
all  the  coloring  matter  is  thrown  down  with  it,  and  forma 
what  is  called  lake.  The  common  lake  used  in  water-color- 
ing is  derived  from  madder  treated  in  this  way.  Carmine 
is  a  lake  made  from  cochineal. 

551.  Silicates  of  Alumina. — This  is  the  most  extensive 
&nd  important  class  of  the  aluminous  salts,  and  comprises  a 
great  number  of  interesting  minerals.      Feldspar,  A1303. 
SSiOg-j-KO.SiOg,  which  is  one  of  the  chief  components  of 
granite  and  granitic  rocks,  is  of  this  class,  and  has  the  com 
position  of  an  anhydrous  alum,  the  sulphuric  acid  being 
replaced  by  the  silicic.    Albite  is  a  salt  having  soda  in  place 
of  the  potash  in  feldspar,  while  spodumene  and  pctalite  are 
similar  compounds,  with  a  portion  of  the  soda  replaced  by 
litliia.     Kyanite  and  andalusite  are  simple  basic  silicates 
of  alumina.     Many  other  similarly  constituted  compounds 
are  found  among  minerals,  some  of  which  are  hydrous  and 
others  anhydrous,  and  varied  by  frequent  substitution  of 
peroxyd  of  iron,  manganese,  or  other  isoniorphous  bases, 
for  the  alumina. 

Plants  do  not  take  up  alumina,  and  it  is  not  yet  proved 
that  their  ashes  ever  contain  it.  Its  value  in  the  soil  seems 
to  be  in  retaining  moisture,  ammonia,  and  carbonic  acid,  and 
in  giving  firmness  to  the  other  incoherent  components  of  the 
soil.  The  decomposition  of  these  silicates  gives  origin  to 
clay,  whose  peculiar  qualities  derived  from  the  alumina  fit 
it  for  the  purpose  of  the  potter. 

This  is  the  place  to  say  a  few  words  upon  the  two  import- 
ant arts  of  glass-blowing  and  pottery. 

Manufacture  of  Glass. 

552.  Silicates  of  Soda. — Both  soda  and  potash  unite  by 
fusion  with  silicic  acid  to  form  silicates  of  variable  compo- 
sition.    If  3  parts  of  the  alkali  are  used  to  1  of  the  silica, 
thn  glass  is  soluble  in  water,  but  whatever  may  be  the  pro- 


What  is  a  mordant  ?  What  a  lake  ?  551.  What  is  the  most  important 
class  of  alumina  compounds  ?  What  is  the  formula  of  feldspar  ?  What 
silicates  are  named?  What  is  the  function  of  alumina  in  soils?  What 
ar.e  clays  ?  552.  How  do  the  alkalies  unite  with  silica.  What  is  the  cha- 
racter of  the  compounds  so  obtained? 


324  METALLIC   ELEMENTS. 

portions  used,  the  resulting  silicate  is  always  an  uncrystal- 
line,  homogeneous,  transparent  mass.  The  "soluble  glass" 
formed  by  fusing  together  8  parts  of  carbonate  of  soda  (or 
10  of  carbonate  of  potash)  with  15  parts  of  pure  sand  and 
1  of  charcoal,  is  insoluble  in  cold,  but  dissolves  in  4  or  5 
parts  of  hot  water,  forming  a  sort  of  varnish,  which  may  be 
applied  to  wood  or  manufactured  stuffs,  which  are  to  a  good 
degree  protected  from  it  by  the  action  of  fire. 

553.  Glass  is   a   variable   compound  of  the  silicates  of 
potash,  soda,  lime,  and   alumina,   with   oxyds  of  lead  and 
iron,  fused  together  by  a  very  high  and  long-continued  heat, 
in  proportions  suited  to  the  object  for  which  the  glass  is  to 
be  used.     The  relation  between  the  oxygen  in  the  base  and 
that  in  the  silica  determines  the  degree  of  fusibility  of  the 
glass :  thus,  the  greater  the  proportion  of  silica  the  less  the 
fusibility  of   glass.      The   principal  varieties  of  glass  are 
these,  viz : 

Window  glass,  a  silicate  of  soda  and  lime,  which  re- 
quires an  intense  heat  for  its  fusion,  and  forms  a  very 
hard  and  brilliant  glass.  Plate  glass,  such  as  is  used  for 
mirrors,  crown  glass  employed  for  glazing,  and  the  beauti- 
ful Bohemian  glass,  are  all  silicates  of  potash  and  lime. 

Crystal  glass  is  formed  by  fusing  together  120  parts  of 
fine  sand,  40  of  purified  potash,  36  of  litharge  or  minium, 
(oxyd  of  lead,)  and  12  of  nitre.  This  forms  a  very  fusible 
glass  easily  worked,  and  so  soft  as  to  be  cut  and  polished 
with  comparative  ease.  The  oxyd  of  lead  greatly  increases 
its  brilliancy. 

Green  bottle-glass  is  usually  a  silicate  of  lime  and  alumina, 
with  oxyds  of  iron  and  manganese,  and  potash  or  soda.  It 
is  formed  of  the  cheapest  refuse  of  the  soap-boiler's  waste, 
and  lime  which  has  been  used  to  make  caustic  potash  or 
soda. 

554.  The  processes  of  the  glass-house  are  all  exceedingly 
interesting  and  instructive — the  tools  few  and  simple — the 
results  dependent  on  the  adroit  manipulations  of  the  work- 
man.    The  materials  are  fused  in  clay  pots,  of  which  seve- 
ral are  heated  in  one  circular  reverberatory  furnace,  their 


What  is  soluble  glass  ?  553.  What  is  glass  ?  What  determines  the 
fusibility  of  glass  ?  What  sorts  are  named  ?  What  is  the  composition 
of  window  and  plate  ?  What  of  crystal  ?  What  of  green  bottle-glass  ? 
654.  How  are  the  materials  fused  ? 


ALUMINUM. 


325 


mouths  outward.  Fig.  363  shows  a  section 
of  one  of  them.  After  two  days  and  nights, 
the  metal,  or  fused  glass,  is  brought  to  a 
homogeneous  condition  and  the  consistence  of 
honey.  The  chief  instrument  of  the  glass- 
blower  is  his  punta  rod,  which  is  simply  an 
iron  tube  a  b,  fig  364,  open  at  both  ends  and 
covered  by  a  wooden  collar  c  d  to  protect  the 
hands  from  the  heat.  This  rod  is  thrust  into 
the  pot  of  molten  glass  while  it  is  turned  in  the  hand,  a 
portion  of  the  fluid  i  A « 

rod  is  withdrawn,  and  Fis-  364' 

if  enough  has  not  adhered  to  meet  the  wants  of  the  work- 
man, he  takes  up  a  second  portion.  This  he  first  fashions 
into  a  cylindrical  form  upon  a 
slab  of  iron,  rolling  the  rod  over 
and  over  in  his  hand,  (fig.  365.) 
Suppose  it  is  required  to  make 
a  glass  tube,  such  as  is  so  much 
used  in  the  laboratory.  He  ap- 
plies his  mouth  to  the  end  of  the  punta-rod  and  blows. 
The  cylinder  of  glass  is  inflated,  .and  assumes  .^^^^k 
a  pear  shape,  as  in  fig.  366.  An  assistant  now  ^^^ 
applies  his  tube,  containing  also  a  small  rigt  366' 
portion  of  hot  glass,  to  the  opposite  extremity  of  the  first 
mass,  (fig.  367,)  and  drawing  against  the  other,  the  ellipti- 


Fig.  365. 


Fig.  367.  Fig.  368. 

cal  mass  is  elongated  and  assumes  the  form  seen  in  fig.  368. 
The  two  workmen  now  walk  rapidly  away  from  each  other  in 
opposite  directions,  drawing  their  tubes  in  the  same  line, 
~ving  the  ductile,  glass  the  form  of  a  tube,  as  seen  in  fig. 
A  few  inches  from  each  punta-tube  the  glass  becomes 


of  a  uniform  size,  the  small  cavity  originally  blown  in  the 


What  are  the  instruments  used?  How  is  a  glass  tube  formed?     Ulus. 
trate  the  process  from  figs.  363-369.     What  is  pressed  glass  ? 


326  METALLIC    ELEMENTS. 

mass  (fig.  3G6)  is  elongated  to  a  smooth  cylindrical  bore,  and 
however  small  the  glass  tube  may  be  drawn  out,  this  bore 
always  remains  circular  and  entire  through  its  whole  length. 
To  fashion  a  bottle,  the  operation  is  commenced  in  the  same 
manner,  but  the  adroitness  of  the  workman  enables  him  to 
elongate  it  by  centrifugal  force,  wheeling  the  molten  mass 
over  his  head  while  he  inflates  it;  and  the  bottom  is  drawn  in 
by  revolving  the  rod  rapidly  on  a  crotch  while  he  applies  the 
surface  of  an  iron  instrument  to  the  revolving  flexible  glass 
to  fashion  it  at  his  will.  Most  of  the  cheap  glass  vessels  now 
manufactured  are  formed  by  blowing  the  glass  in  a  metallic 
mould  opening  in  two  parts.  This  is  called  pressed  glass. 
In  the  laboratory  a  flat  lamp,  like  fig.  370,  fed  with  tallow, 

is  employed  to  fashion  tubes 
into  the  various  forms  re- 
quired for  the  construction 
of  the  apparatus.  The  flame 
is  driven  by  a  bellows  under 
the  table  worked  by  the  foot. 
With  a  little  practice,  the 
operator  soon  acquires  suf- 
ficient skill  to  make  from  plain  tubes  such  forms  of  glass 
apparatus  as  are  figured^in  this  work. 

All  glass  must  be  carefully  annealed  after  it  is  made,  by 
slow  cooling,  or  it  will  break  in  pieces  with  the  least  scratch 
or  jar.       Slow  cooling  of   heated  glass  for  many  hours,  or 
even  days,  is  required  for  heavy  articles.     Prince  Rupert's 
/""   drops  (fig.  371)  are   little  tears  of  glass  dropped 
/        into  water  when  fused.    The  outer  surface  becom- 
//  ing  solid  while  the  inner  parts  are  still  flexible, 

|A  there  comes  to  be  an  enormous  strain  on  the  ex- 

^f  terior,  due  to  the  contraction  at  the  centre.  If  the 

Fig.  371.  little  end  of  this  tear  is  broken,  the  whole  sud- 
denly and  with  an  explosion  flies  into  dust.  Unannealed 
glass  is  to  a  certain  degree  under  the  same  conditions  of 
unequal  tension.  Hence  the  necessity  of  annealing  or  slow 
cooling  to  give  time  for  the*  particles  to  rearrange  them- 
selves without  strain.  Glass  is  colored  red  by  the  oxyds  of 
copper  and  gold,  blue  by  oxyds  of  cobalt,  white  by  tin, 


How  is  glass  worked  in  the  laboratory  ?  What  is  annealing?  How  is 
this  illustrated  by  Prince  Rupert's  drops  ?  Explain  the  illustration.  How 
is  glass  colored  ? 


ALUMINUM.  827 

arsenic  and  antimony,  yellow  by  uranium,  purple  and  violet 
by  manganese,  and  green  by  chromium,  iron,  nickel,  &c. 
By  the  skilful  use  of  these  oxyds,  with  a  heavy  and  highly 
refracting  glass,  the  various  gems  are  very  beautifully  imi- 
tated. Such  imitations  are  called  pastes. 

Pottery. 

555.  One  of  the  oldest  of  human  inventions  is  the 
fashioning  of  vessels  of  use  and  ornament  out  of  clay.  The 
bricks  of  Babylon  and  Nineveh,  covered  with  arrow-head 
inscriptions,  are  among  the  most  ancient  memorials  of 
history. 

The  decomposition  of  feldspar  and  other  aluminous  mine- 
rals and  rocks  gives  origin  to  the  clays  which  are  so  import- 
ant in  the  art  of  pottery.  Decomposed  feldspar  forms 
porcelain  clay,  commonly  called  kaojin.  The  undecom- 
posed  mineral  is  often  ground  up  to  mix  with  the  materials 
for  porcelain.  The  difference  between  porcelain  and  earthen- 
ware consists  in  the  partial  fusion  of  the  materials  of  the 
former  by  the  heat  of  the  furnace,  which  gives  it  the  semi- 
transparency  and  great  beauty  for  which  it  is  so  highly 
prized.  Common  earthenware  is  often  glazed  with  oxyd 
of  lead,  an  unsafe  mode  for  culinary  vessels  :  common  salt 
(508)  is  also  used,  being  raised  in  vapor  by  the  heat  of  the 
kiln.  The  soda  unites  with  silica,  while  the  chlorine  escapes 
as  chlorid  of  iron.  The  glaze  in  porcelain  is  formed  of  a 
more  fusible  mixture  of  the  same  materials,  put  over  the 
articles  as  a  wash,  after  they  have  been  once  through  the 
furnace,  (in  which  state  they  are  called  biscuit  ware;)  they 
are  then  baked  again  at  a  heat  which  fuses  the  glaze,  but 
which  does  not  soften  the  body  of  the  ware.  All  porcelain  is 
twice  fired  and  sometimes  thrice.  If  painted,  the  design  is 
laid  upon  the  surface  in  colors  formed  from  metallic  oxyds, 
which  develop  th'eir  appropriate  tints  only  after  fusion  with 
the  ingredients  of  the  glaze.  Metallic  gold  is  put  on  in  the 
form  of  an  oxyd,  and  the  steel  lustre  is  produced  by  metal- 
lic platinum.  This  beautiful  art  is  carried  to  a  wonderful 


How  made  refractive?  555.  What  is  one  of  the  most  ancient  arts? 
Whence  is  potter's  clay  derived  ?  What  is  kaolin  ?  What  is  the 
difference  between  porcelain  and  earthenware  ?  How  is  pottery  glazed  ? 
How  porcelain  ?  How  painted  ? 


328  METALLIC   ELEMENTS. 

perfection  in  the  royal  establishments  of  France  and  Prus- 
Bia,  where  the  first  talent  is  employed  in  modelling  and  paint- 
ing. Any  further  detail  of  these  interesting  branches  of 
applied  chemistry  would  be  out  of  place  here,  and  the  stu- 
dent is  referred  to  larger  works  for  a  fuller  description. 

556.  There  are  six  other  metals  belonging  to  this  class, 
which  are  so  rare  and  comparatively  unimportant  that  we 
pass  them  with  the  most  cursory  enumeration :    Glucinum 
is  the  base  of  a  sesquioxyd  G30S,  (glucina,)  which  is  the 
characteristic  earth  of  the  emerald,  beryl,  and  chrysoberyl, 
It  is  very  like  alumina,  and  is  named  in  allusion  to  tho 
sweet  taste  of  its  salts.      Yttrium  is  the  metal  of  the  earth 
yttria  YO,  found   in   the  minerals   yttrocerite,  &c.     Zir- 
conium is  found  as  a  sesquioxyd  of  zirconia  Zr^  in  zircon. 
Thoria  was  found  by  Berzelius  in  the  rarest  of  all  minerals, 
the  thorite,  of  Sweden.    Thorium  has  the  highest  specific 
gravity  (9)  of  any  eftrth.      Cerium  and    lantanium  are  in- 
variably associated,  and  with  them  another  rare  metal,  didy- 
mium.     The  minerals  ccritc,  allanite,  and  monazite  contain 
them. 

CLASS  IV.    HEAVY  METALS,  WHOSE  OXYDS  FORM 
POWERFUL  BASES. 

MANGANESE. 
Equivalent,  2 7 -6.      Symbol,  Mn.     Density,  8. 

557.  Manganese  is  never  found  as  a  metal  in  nature,  but 
may  be  produced  from  its  black  oxyd  by  a  high  heat  with 
charcoal.     Metallic  manganese  is  a  gray,  brittle  metal,  not 
magnetic,  and  resembles  some  varieties  of  cast-iron.     It  dis- 
solves rapidly  in  sulphuric  acid  with  escape  of  hydrogen. 

Manganese,  in  the  form  of  the  black  oxyd,  is  an  important 
and  pretty  common  metal.  Its  great  use  is  for  producing 
chlorine  (282)  and  in  the  manufacture  of  glass,  where  it 
acts  by  its  oxygen  to  decolorize  the  compound. 

558.  We  enumerate  five  compounds  of  manganese,  viz. 
protoxyd  MnO ;  sesquioxyd  (or  braunite)  Mn30., ;  peroxyd, 
or  deutoxyd,  (pyrolusite,)  Mn02;    manganic  acid   Mn03; 
hypermanganic  acid  Mn307. 

656.  Enumerate  the  other  earthy  metals  named  in  this  section.  557. 
What  are  the  equivalent  and  properties  of  manganese  ?  What  form  of  it  ia 
most  common  ?  For  what  is  it  used  ?  558.  How  many  and  what  oxydi 
yf  manganese  are  named? 


MANGANESE.  329 

The  protoxyd  is  a  green-colored  powder,  formed  from 
heating  the  carbonate  of  manganese  in  an  atmosphere  of 
hydrogen.  It  is  a  powerful  base,  attracts  oxygen  from  the 
air,  and  is  the  base  of  the  beautiful  rose-colored  salts  of 
manganese. 

The  sesquioxyd  or  Iraunite  occurs  crystallized  in  octahe- 
drons and  forms  belonging  to  the  dimetric  system. 

The  hydra  ted  sesquioxyd  Mn303+H0  (manganite)  is  a 
finely  crystallized  mineral,  in  long  black  prisms,  found  in 
superb  specimens  at  Ilfeld,  in  the  Hartz.  In  powder  the 
sesquioxyd  is  brown  ;  it  is  decomposed  by  chlorohydric  acid 
•with  the  evolution  of  chlorine,  but  sulphuric  acid  combines 
with  it  to  form  a  sesquisulphate,  which  yields  a  purple 
double  salt  with  sulphate  of  potash,  (manganese  alum,)  iso- 
morphous  with  the  corresponding  salt  of  alumina. 

559.  The  peroxyd  Mn02  is  the  most  common  and  most 
valuable  ore  of  manganese.    From  it  we' obtain  oxygen,  and, 
by  the  decomposition  of  chlorohydric  acid,  chlorine.     It  is 
found  abundantly  at  Bennington,  Vermont,  and  other  places 
in  this  country.     When  crystallized  it  is  called  pyrolusite. 
Beautiful  specimens  of  this  mineral  have  been  observed  at 
Salisbury  and  Kent,  Connecticut,  among  the  iron  ores. 

560.  Manganic  acid  is  known  only  in  combination,  espe- 
cially as  manganate  of  potash.     This  is  best  formed  by  mix- 
ing equal  parts  of  finely  powdered  black  oxyd  of  manganese 
and  chlorate  of  potash  with  rather  more  than  one  part  of 
hydrate  of  potash  dissolved  in  a  very  little  water.     This 
mixture,  when  evaporated,  is  heated  to  a  point  short  of  red- 
ness, and  a  dark  green  mass  is  formed  which  contains  man- 
ganate of  potash.    In  this  case  the  manganese  obtains  oxygen 
from  the  chlorate  of  potash,  and  the  manganic  acid  thus 
formed  combines  with  potash,  giving  a  salt  in  green  crystals. 
This  salt,  dissolved  in  water,  gives  a  brilliant  emerald-green 
solution,  which  almost  immediately  changes  color,  being  in 
quick  succession  green,  blue,  purple,  and  finally  crimson- 
red,  and  has  thence  been  called  chameleon  mineral.     This 
last  color  is  due  to  the  presence  of  permanganic  acidj  which, 
however,  cannot  be  separated   from  its  combinations,  but 

Which  is  the  base  of  the  rose-colored  salts  ?  What  is  the  sesquioxyd  ? 
Give  the  formula  of  the  hydrated  sesquioxyd?  What  is  said  of  the  sul- 
phate of  the  sesquioxyd?  559.  Which  is  the  most  common  ore  of  man- 
ganese? Where  and  how  is  it  found?  560.  Describe  manganic  acid  and 
the  salt  it  forms  with  potash.  What  is  the  changeable  compound  called? 


330  METALLIC   ELEMENTS. 

forms  a  salt  with  potash  in  beautiful  purple  crystals.  The 
compounds  of  permanganic  acid  are  more  stable  than  the 
manganates.  The  salts  of  these  acids  are  respectively  iso- 
morphous  with  sulphates  and  perchloratcs  S03  and  ClaOr 

561.  The  clilorids  of  manganese  MnCl  and  Mn3Cl3  cor- 
respond to  the  protoxyd  and  sesquioxyd.     The  chlorid  is 
formed  abundantly  in  acting  on  black  oxyd  of  manganese 
(282)  with  hydrochloric  acid.     The  mixed  solution  of  chlo- 
rids  of  iron  and  manganese  is  evaporated  to  dryness,  and 
then  heated  to  dull  redness.     The  chlorid  of  manganese  is 
then  dissolved  out  from  the  dry  mass,  leaving  the  insoluble 
protoxyd  of  iron  behind.     It  has  a  beautiful  pink  tint,  and 
deposits  tabular  rose-colored  crystals  on  evaporation.     It  is 
soluble  in  alcohol,  and  fusible  by  heat. 

562.  The  salts  of  manganese  are   numerous,  and  in  a 
chemical  view  quite  important.     Sulphate  of  manganese 
MnO.S03-f-7HO  is  a  very  beautiful  rose-colored  salt,  iso- 
morphous  with  sulphate  of  magnesia.     It  is  used  to  give 
a  fine  brown  dye  to  cloth,  being  decomposed  by  a  solution 
of  bleaching-powder,  which  forms  the  brown  peroxyd  in  the 
fibre  of  the  stuflfe.     It  is  also  used  in  medicine. 

Potassa  and  soda  throw  down  the  oxyd  of  manganese  as  a 
white  powder,  which  immediately  turns  brown  from  the  forma- 
tion of  a  higher  oxyd.  The  carbonates  of  the  alkalies  throw 
down  carbonate  of  manganese  from  their  soluble  salts.  Any 
compound  of  manganese  fused  upon  a  slip  of  platina  with 
carbonate  of  soda,  gives  a  powerfully  characteristic  green  salt, 
the  permanganate  of  soda. 

IRON. 

Equivalent,  28.     Symbol,  Fe.     Density,  7-8. 

563.  Iron  is  found  malleable,  and  alloyed  with  nickel,  in 
large  masses  of  meteoric  origin.    One  of  these,  discovered  in 
Texas,  weighs  1635  pounds,  and  is  now  in  Yale  College 
cabinet.     It  is  not  certain  that  malleable  iron  of  terrestrial 
origin  has  yet  been  discovered  in  nature.     Iron  is  the  most 
abundant  and  most  useful  metal  known  to  man.     Its  ores 


What  is  said  of  the  salts  of  manganic  and  permanganic  acid?  561. 
Describe  the  chlorids  of  manganese  ?  562.  What  is  said  in  general  of 
the  salts  of  manganese?  What  tests  are  named  for  manganese  and  it,s 
salts?  563.  What  is  the  equivalent  of  iron?  How  is  malleable  iron 
found  ?  What  is  said  of  its  abundance  and  value  ? 


IRON.  odl 

are  found  everywhere,  and  often  in  immediate  connection 
with  the  coal  and  limestone  necessary  to  reduce  them  to  the 
metallic  state.  There  is  no  soil,  and  scarcely  any  mineral, 
which  does  not  contain  some  proportion  of  the  oxyd  of  iron. 
We  know  iron  as  malleable  iron,  steel,  and  cast  iron. 

564.  To  obtain  pure  iron  is  not  easy,  and  the  best  iron  of 
commerce  is  always  contaminated  with  carbon  and  silicon. 
Small  quantities  of  iron  are  prepared  absolutely  pure,  in  the 
laboratory,  by  reducing  the  pure  oxyd  of  iron  in  a  bulb  of  hard 


Fig.  372. 

glass  a  b  (fig.  372)  by  a  current  of  dry  hydrogen.  The  bulb 
A  is  heated  by  the  flame  of  a  spirit-lamp.  This  apparatus 
serves  for  numerous  reductions  of  metallic  oxyds,  as,  for 
example,  the  oxyds  of  cobalt,  nickel,  zinc,  &c.  The  bulbed 
tube  a  b  is  drawn  down  at  c  (fig.  373)  to  a  narrow  neck, 
so  that  while  the  tube  is  yet  A 

full  of  hydrogen  it  may  be  seal- 
ed by  the  blowpipe  both  at  c 
and  b:  otherwise  the  pulverulent  Fig.  373. 

metallic  iron,  from  its  strong  afiinity  for  oxygen,  will  take 
fire  on  contact  of  air,  and  be  carried  back  again  to  its  original 
condition  of  oxyd.  If  this  operation  is  conducted  in  a  por- 
celain tube  at  a  high  heat,  the  iron  formed  assumes  a  metallic 
lustre,  and  does  not  oxydize ;  and  if  protochlorid  of  iron  is 
used  in  place  of  the  oxyd,  the  metal  rises  in  vapor,  lining 
the  tube  with  a  brilliant  crystalline  crust. 

565.  When  quite  pure,  it  is  nearly  white,  quite  soft,  per 
fcctly  malleable,  and  the  m*st  tenacious  of  all  metals,  (471.) 
Its  density  is  7-8,  which  may  be  a  little  increased  by  ham- 

564.  How  is  pure  iron  obtained?  Describe  fig.  372.  What  happens 
if  the  iron  so  obtained  is  exposed  to  air  ?  How  is  it  obtained  more  dense  1 
665.  What  are  its  properties  ? 


S32  METALLIC   ELEMENTS 

naering.  It  crystallizes  in  forms  of  the  first  class,  a:>  is* 
beautifully  shown  in  the  crystalline  structure  of  the  meteoric 
iron,  and  sometimes  in  the  crust  produced 
in  the  reduction  of  the  protochlorid.  It 
fuses  with  extreme  difficulty,  first  becom- 
ing soft  or  pasty,  in  which  state  it  is 
welded.  When  intensely  heated  in  air 
or  oxygen  gas  it  combines  with  oxygen, 
burning  with  brilliant  light  and  numerous 
scintillations,  and  is  converted  into  oxyd 
of  iron,  (fig.  374.)  Iron  also  attracts 
oxygen  from  the  air  at  common  tempera- 
tures, forming  rust.  This  does  not  happen  in  dry  air,  but 
the  presence  of  moisture,  and  particularly  of  a  little  acid 
vapor,  very  much  promotes  its  formation.  Iron  decomposes 
water  very  rapidly  at  a  red-heat,  hydrogen  being  evolved. 
Its  magnetic  relations  have  already  been  fully  explained. 
Cobalt  and  nickel  are  the  only  other  magnetic  metals. 

566.  The  oxyds  of  iron  arc  three,  viz  :  1.  Protoxyd, 
FeO;  2.  Sesquioxyd,  commonly  called  peroxyd,  Fe303; 
3.  Ferric  acid,  Fe03.  The  magnetic  oxyd  Fe304  is  regarded 
as  a  compound  of  protoxyd  and  sesquioxyd  FeO.Fe303,  in 
which  the  sesquioxyd  plays  the  part  of  a  base,  (475.) 

1.  The  protoxyd  of  iron  FeO  is  a  powerful  base  which 
is  unknown  in  nature  except  in  combination.     It  saturates 
acids  completely  and  is  isomorphous  with  a  lar^e  class  of 
bodies,  of  which  zinc  and  magnesia  are  examples,  (263.) 
This  oxyd  is  thrown  down  from  its  solutions  by  potash,  as 
a  whitish  bulky  hydrate,  that  soon  gains  another  portion 
of  oxygen  from  the  air,  becoming  brown,  and  finally  red. 
Its  salts,  when  soluble,  have  a  styptic  taste  like  ink,  and  a 
greenish  color,  of  which  the  most  familiar  example  is  green 
vitriol,  or  sulphate  of  protoxyd  of  iron. 

2.  The  peroxyd  of  iron  Fe203  is  found  native  in  the 
beautiful  specular  iron  of  Elba,  and  also  in  the  red  and 
brown  hematites.     Limonite  2(Fe203)-(-3HO  is  a  hydrous 
sesquioxyd.     It  is   slightly  acted   on  by  the  magnet,  and 
after  ignition  is  almost  insolublesn  strong  acids.     It  is  iso- 
morphous with  alumina,  and  is  generally  associated  with  it 
in  soils  and  many  minerals.     It  is  often  of  a  brilliant  red, 


What  is  welding?    566.  What  oxyds  are  named  ?    Give  their  formulas. 
Describe  the  protoxyd  and  its  salts.     How  is  the  peroxyd  known  ? 


IRON.  833 

and,  as  ochre  of  various  tints,  is  much  used  as  a  pigment. 
Ammonia,  potassa,  or  soda  precipitates  it  from  its  solutions 
as  a  bulky  red  hydrate,  which,  in  its  moist  condition,  is 
esteemed  an  antidote  to  poisoning  by  arsenic.  Colcothar, 
or  rouge,  is  this  oxyd  prepared  by  calcining  the  sulphate  :  it 
is  much  used  in  polishing  metals. 

Magnetic  oxyd  of  iron  Fe304  is  familiarly  known  in  the 
common  magnetic  iron  ore  and  native  lode-stone.  It  crys- 
tallizes in  octahedrons.  It  forms  no  salts,  and,  as  has  al- 
ready been  remarked,  is  regarded  as  a  salt  of  FeO-}-Fe303. 
The  finery  cinders  or  scales  thrown  off  under  the  smith's 
hammer  are  this  oxyd. 

3.  Ferric  Add,  Fe03. — This  compound,  discovered  by  M. 
Fremy,  corresponds  to  manganic  acid.  Ferrate  of  potash  is 
formed  when  one  part  of  peroxyd  of  iron  and  four  parts  of 
nitre  are  heated  to  full  redness  in  a  covered  crucible  for  an 
hour.  The  ferrate  of  potash  is  dissolved  out  of  the  porous 
mass  by  ice-cold  water.  The  solution  has  a  deep  amethyst- 
ine color,  and  is  easily  decomposed  by  heat.  A  soluble 
salt  of  baryta  precipitates  ferric  acid  as  a  beautiful  red  fer- 
rate of  baryta,  which  is  permanent. 

567.  The  chlorids  of  iron  Fed  and  Fe3Cl3  correspond  to 
the  protoxyd  and  sesquioxyd  of  the  same  base.     The  per- 
chlorid  is  often  used  in  medicine,  and  may  be  formed  by 
saturating  hydrochloric  acid  with  freshly  prepared  peroxyd 
of  iron.     The  protiodid  of  iron  is  also  a  valuable  medicine. 

The  sulphurets  of  iron  are  found  in  nature,  and  are  known 
under  the  mineralogical  names  of  pyrites  and  marcasite 
FeS3,  and  magnetic  pyrites  Fe7Ss.  The  protosulphuret  FeS 
is  easily  formed  artificially,  by  fusing  sulphur  with  iron 
filings :  they  ignite  with  a  vivid  combustion,  and  proto- 
sulphuret of  iron  is  formed,  which  is  much  used  in  pre- 
paring sulphuretted  hydrogen.  Yellow  iron  pyrites  and 
white  iron  pyrites  (marcasite)  are  dimorphous  forms  of  the 
bisulphuret  FeS3 :  the  first  is  one  of  the  most  common  of 
crystallized  minerals. 

568.  Of  the  salts  of  iron,  green  vitriol,  or  copperas,  a  pro- 


What  is  colcothar  ?  Give  the  formula  of  the  black  oxyd.  How  is  it  found 
in  nature  ?  What  is  ferric  acid  ?  567.  What  chlorids  of  iron  are  named  ? 
What  oxyds  do  they  correspond  to  ?  What  are  the  sulphurets  of  iron  ? 
For  what  is  the  protosulphuret  used  ?  What  is  the  name  of  the  ordinary 
sulphuret  ?  What  two  forms  of  it  are  found  in  nature  ? 


334  METALLIC   ELEMENTS. 

tosulphate  FeO.S03-f-7HO,  is  the  most  important.  It  is 
made  in  immense  quantities,  as  at  Stafford,  Vt ,  from  the 
fermentation  of  iron  pyrites,  which  furnishes  both  the  acid 
and  the  base.  This  salt  crystallizes  beautifully,  and  is 
much  used  as  the  basis  of  all  black  dyes  and  of  ink,  and  in 
the  manufacture  of  prussian  blue.  Persulphate  of  iron  is  a 
sulphate  of  the  peroxyd  Fe303-f-3S03.  Carbonate  of  iron 
occurs  in  nature  as  spathic  iron  ore,  which  is  isomorphous 
with  carbonate  of  lime.  A  variety  of  steel  is  made  directly 
from  this  ore  without  cementation,  (570.)  It  is  formed 
artificially  by  precipitating  a  solution  of  protosulphate  by 
an  alkaline  carbonate.  It  is  used  in  medicine. 

Water  containing  carbonic  acid  dissolves  protoxyd  of  iron 
and  acquires  the  well-known  flavor  of  chalybeate  waters : 
exposure  to  air  permits  the  escape  of  the  carbonic  acid, 
when  the  iron  falls  as  red  peroxyd. 

Phosphate  of  iron  FeO.P05-j-8HO  is  formed  as  a  green- 
ish-white gelatinous  precipitate  when  solution  of  tribasic 
phosphate  of  soda  is  added  to  solution  of  protosulphate  of 
iron.  It  is  an  article  of  the  materia  medica.  Vivianite 
is  a  mineral  having  the  same  formula,  found  both  massive 
and  crystallized,  of  a  beautiful  indigo-blue  color. 

The  cyanogen  compounds  of  iron  will  be  described  in  the 
organic  chemistry. 

The  presence  of  a  salt  of  iron  is  easily  detected  by  the 
fine  blue  (prussian  blue)  formed  on  adding  prussiate  of 
potash  to  the  solution :  an  infusion  of  galls  gives  a  black 
color  (ink)  to  solutions  of  iron  salts. 

569.  The  chief  ores  of  iron  are,  1.  The  specular  iron  or 
peroxyd,  including  red  and  brown  hematite;  2.  Limonite,  or 
hydrous  peroxyd,  from  which  the  best  iron  is  made — (bog 
iron  also  comes  under  this  head;)  3.  Clay  iron-stone,  which 
is  an  impure  carbonate  of  iron,  or  carbonate  of  iron  with 
carbonate  of  lime  and  magnesia — this  is  the  nodular  ore  and 
band  ore  of  the  coal  formations ;  4.  Black  or  magnetic  oxyd 
of  iron,  which  is  the  ore  of  the  iron  mountains  of  Missouri 
and  of  Sweden. 

The  reduction  of  the  ores  of  iron  to  the  metallic  state  is 
usually  performed  in  large  furnaces  called  hujh  or  blast  fur- 

568.  Which  of  the  salts  of  iron  is  of  great  importance?  How  and 
where  is  it  made  in  this  country?  What  is  the  carbonate  and  for  what 
used?  What  of  the  phosphate?  What  tests  are  named  for  iron  ?  569.  What 
ores  of  iron  are  enumerated?  How  is  the  reduction  of  iron  effected? 


IRON. 


335 


naces.  These  are  built  of  stone, 
in  a  conical  form,  30  to  50  feet 
high,  and  lined  internally  with 
the  most  refractory  fire-bricks. 
The  furnace  is  divided  into  the 
throat,  the  fire-room  b,  the 
boshes  ey  (that  portion  sloping 
inward,)  the  crucible  t,  and 
the  hearth  h.  The  blast  of 
air — supplied  from  very  large 
blowing  cylinders — is  intro- 
duced by  two  or  three  tuyere . 
pipes  a  a,  near  the  bottom.  In 
the  most  improved  furnaces,  the 
air-blast  is  heated  by  causing  a 
it  to  pass  through  a  series  of 
pipes  in  the  upper  portion  of  the 
furnace,  so  as  to  have  a  temper-  Fig.  375. 

ature  of  500°  or  more  when  it  enters  the  furnace.  When 
the  furnace  is  brought  into  action,  it  is  first  heated  with 
coal  only,  for  about  24  hours,  to  raise  it  to  the  proper  tem- 
perature \  and  then  is  charged  alternately  with  proper  pro- 
portions of  coal,  roasted  ore,  and  lime  for  flux,  until  it  is 
quite  full.  When  once  brought  into  action,  the  blast  is 
kept  up  for  months  or  even  years,  until  the  furnace  requires 
repairing.  The  ore  is  reduced  on  the  boshes,  and  in  the 
upper  part  of  the  crucible,  where  the  oxyd  of  carbon  is  found 
almost  pure  in  presence  of  an  excess  of  white-hot  carbon  and 
ore  previously  dried  and  in  part  reduced  in  the  higher  parts 
of  the  furnace.  The  melted  metal  collects  on  the  hearth, 
where  it  rests,  covered  by  the  molten  flux,  which  is  a  glass, 
formed  by  the  fusion  of  the  lime  used,  with  the  earthy  parts 
of  the  ore.  From  time  to  time,  the  iron  is  drawn  off  by  an 
opening  level  with  the  hearth,  previously  stopped  with  clay, 
and  run  into  rude  open  moulds  in  sand.  This  is  cast  iron, 
and  is  of  various  qualities,  according  to  the  various  charac- 
ter of  the  ore  and  the  working  of  the  furnace.  If  malle- 
able bar  iron  is  wanted,  the  cast  iron  is  again  melted,  in 
what  is  called  the  puddling  furnace,  where  it  is  stirred 


Describe  the  high  furnace.  What  is  the  hot  blast?  What  is  the  ope- 
ration  of  the  furnace  ?  What  is  cast  iron  ?  How  is  malleable  iron  made 
from  cast  iron  ? 


336  METALLIC   ELEMENTS. 

about  by  an  iron  rod,  in  contact  with  oxyd  of  iron,  and  a 
current  of  heated  carbonic  oxyd  from  burning  wood  or  coal. 
It  gradually  becomes  stiff  and  pasty  from  the  burning  out 
of  the  carbon,  and  from  some  molecular  change  not  well 
understood.  This  pasty  condition  increases  until  the  iron 
is  finally  raised  in  a  rude  ball  and  placed  under  the  blows 
of  a  huge  tilt-hammer,  when  the  scoria  is  pressed  out  and 
the  particles  made  to  cohere.  It  grows  tenacious  by  a  repe- 
tition of  this  process,  being  cut  up  and  piled  or  faggoted  and 
reheated  several  times,  until  it  is  finally  rolled  in  the  roll- 
ing-mill into  tough  and  fibrous  metal. 

570.  Steel  is  formed  from,  refined  iron  by  heating  it  for 
days  in  succession  in  contact  with  charcoal  in  close  vessels, 
(called  cementation.)  It  gains  from  one  to  two  per  cent 
of  carbon,  becomes  fusible,  and  can  be  tempered  according 
to  the  use  for  which  it  is  designed. 

The  Catalan  forge  is  a  furnace  formed  like  a  smith's  forge 
on  a  large  scale,  and  in  which  the  circumstances  of  the  high 
and  puddling  furnace  are  combined,  so  that  malleable  iron 
is  produced  from  the  ore — the  cast  iron  being  brought  to 
the  ductile  state  in  the  same  fire  where  it  is  reduced  from 
the  ore — charcoal  is  the  fuel  of  the  Catalan  forge.  The 
best  iron  is  always  produced  when  charcoal  is  the  fuel,  being 
free  from  sulphur  and  phosphorus,  the  two  worst  enemies 
of  good  iron. 

CHROMIUM. 
Equivalent,  264.      Symbol,  Cr.     Density,  6. 

571.  Chromium  in  combination  with  iron  is  rather  an 
abundant  substance,  particularly  in  this  country,  being  found 
as  chromic  iron  at  Barehills,  near  Baltimore ;  Lancaster  Co., 
Pa.,  and  in  several  other  places.  The  beautiful  red  chro- 
mate  of  lead  is  also  a  natural  product  in  Siberia.  The 
metal,  from  its  great  affinity  for  oxygen,  is  very  difficult  to 
procure.  It  is  a  hard,  almost  infusible  substance,  resem- 
bling cast  iron,  nearly  insoluble  in  acids,  and  does  not 
decompose  water.  It  may  be  oxydized  by  fusion  with  nitre, 
but  does  not  change  in  the  air. 

570.  What  is  steel?  What  is  the  Catalan  forge?  What  fuel  makes 
the  best  iron  ?  571.  What  are  the  symbol  and  properties  of  chromium  ? 
How  distributed  in  nature  ? 


CHROMIUM.  337 

572.  The  oxyds  of  chromium  are  exactly  the  same  as 
those  of  manganese.    Chromium  bears  the  strongest  analogy 
in  its  chemical  character  to  manganese  and  iron.     The  pa- 
rallelism of  constitution  in  the  oxyds  of  these  three  metals 
is  shown  in  the  following  tabular  arrangement : — 

Acids. 
Protoxyd.     Sesqxiioxyd.    Black  oxyd.    Peroxyd.  , *  > 

Manganese  forms.. MnO  ...  Mna03  ...  Mn,04  ...  MnOa     MnO,     Mn,0t 

Iron  forms FeO    ...  Fe,03    ...  Fe304    ...  FeO, 

Chromium  forms... CrO    ...  Cra03     ...   Cr,04     ...  CrOa       CrO,       Cr.O, 

The  protoxyd  of  chromium  is  a  strong  base,  acting  in 
combination  like  the  protoxyd  of  iron,  with  which  it  is  iso- 
morphous. 

573.  Sesquioxyd  of  chromium  Cr203  may  be   obtained 
in  little  rhornbohedral  crystals  by  passing  the  vapor  of  chlo- 
rochromic  acid  through  a  heated  tube,  2Cr03Cl  =  Cr303-f- 
201-j-O.     The  crystals  are  deposited  on  the  walls  of  the 
tube  in  a  brilliant  deep-green  crust.     They  are  as  hard  as 
ruby.     Their  density  is  5-21. 

The  hydrated  sesquioxyd  of  chromium  Cra03-j-HO  is 
easily  prepared  by  treating  a  boiling  and  rather  dilute  solu- 
tion of  bichromate  of  potash  with  an  excess  of  chlorohydric 
acid,  and  then  wi^h  successive  portions  of  alcohol  or  sugar 
until  it  assumes  a  fine  emerald  tint.  Ammonia  throws  down 
a  bulky,  pale-green  precipitate,  soluble  in  acids  and  shrink- 
ing very  much  in  drying — this  is  the  hydrate.  On  ignition 
it  undergoes  vivid  incandescence  and  becomes  deep  green. 
The  sesquioxyd  of  chromium  is  a  feeble  base  like  those  of 
iron  and  alumina,  and  may  replace  them  in  combination,  as 
in  the  formation  of  chrome  alum  with  sulphate  of  potash. 
Sesquioxyd  of  chromium  forms  an  alum  also  with  the  sul- 
phates of  soda  and  ammonia.  All  the  salts  of  this  oxyd 
are  either  emerald  green  or  bluish  purple.  It  imparts  a 
rich  tint  of  green  to  glass  and  porcelain,  and  is  the  cause 
of  the  color  of  the  emerald.  Chrome  iron  is  composed  of 
this  oxyd  and  protoxyd  of  iron  FeO.Cr203,  isomorphous  with 
magnetic  iron  FeO.Fe303,  and  with  spinel  MgO.Al203.  The 
chrome  iron  of  Pennsylvania  contains  a  little  nickel. 

574.  Chromic  acid  Cr03  is  readily  formed  by  treating 

572.  What  strong  analogies  has  it  ?  Give  the  parallel  oxyds  of  Mn,  Fe, 
and  Cr.  573.  How  is  sesquioxyd  of  Cr  obtained  ?  How  is  its  hydrate  ? 
What  are  its  properties  ?  What  salts  does  it  form  ?  What  is  chrome  iron  ? 
574.  How  is  chromic  acid  formed? 

22 


338  METALLIC   ELEMENTS. 

a  cold  and  concentrated  solution  of  bichromate  of  potash 
with  one  and  a  half  parts  of  sulphuric  acid.  The  mixture, 
when  cold,  deposits  brilliant  ruby-red  prisms  of  chromic 
acid.  The  sulphato  of  potash  in  solution  above,  may  be 
turned  off,  and  the  chromic  acid  dried  on  a  porous  brick, 
being  carefully  covered  with  a  glass  to  prevent  access  of 
organic  matters,  which  at  once  decompose  it.  If  a  little  of 
this  acid  be  thrown  into  alcohol  or  ether,  the  violence  of  the 
action  is  such  as  to  set  fire  to  the  mixture.  Chromic  acid 
forms  numerous  salts,  which  are  highly  colored. 

The  protochlorid  of  chromium  CrCl  is  obtained  as  a 
white  and  very  soluble  substance  by  the  action  of  dry  hy- 
drogen gas  on  the  sesquichlorid.  The  sesquichlorid  Cr3Cl8 
is  prepared  by  passing  chlorine  gas  over  an  ignited  mixture 
of  the  sesquioxyd  and  charcoal.  It  forms  a  crystalline 
sublimate  of  a  peach-blossom  color,  which  is  insoluble  in 
water.  The  sesquioxyd  dissolves  in  chlorohydric  acid, 
but  the  hydrated  chlorid  thus  obtained  is  decomposed  by 
heat. 

Chlorochromic  acid  Cr03Cl  is  a  deep-red  volatile  liquid, 
much  resembling  bromine  in  its  appearance.  It  is  formed 
when  10  parts  of  common  salt  and  17  of  bichromate  of 
potash  are  intimately  mixed,  and  heated  in  a  retort  with 
30  parts  of  concentrated  sulphuric  acid.  The  chlorochromic 
acid  distils  over,  filling  the  receiver  with  a  superb  ruby-red 
vapor.  Its  density  is  1-71,  and  it  boils  at  248°.  Water 
decomposes  it,  forming  chromic  and  hydrochloric  acids.  It 
may  be  preserved  in  tubes  hermetically  sealed. 

575.  The  chromate  and  the  bichromate  of  potash  are  both 
familiar  compounds  of  chromic  acid.  The  first,  KO.Cr03,  is 
formed  on  a  very  large  scale,  by  decomposing  the  native 
chromic  iron  with  nitrate  of  potash,  by  aid  of  heat.  Chro- 
mate of  potash  is  dissolved  out  from  the  ignited  mass,  and 
crystallizes  in  anhydrous  yellow  crystals.  It  is  isomorphous 
with  sulphate  of  potash,  dissolves  in  two  parts  of  cold  water, 
and  is  the  source  of  all  the  preparations  of  chromium. 

Bichromate  of  potash  K0.2Cr03  is  formed  by  adding 
sulphuric  acid  to  a  solution  of  the  yellow  chromate,  when 
half  the  potash  is  removed,  and  the  bichromate  crystallizes 


Give  its  properties.  Describe  the  chlorids  of  chromium.  Describe  chlo. 
rochromic  acid.  575.  How  is  chromate  of  potash  formed  ?  How  is  bi- 
chromate of  potash  formed  ? 


NICKEL.  339 

by  slow  evaporation  in  brilliant  red  crystals  of  a  rhombic 
form,  which  are  soluble  in  ten  parts  of  cold  water. 

576.  ChromateofLead—ChromeYdlow — (PbO.Cr03)  is 
the  well-known  pigment  prepared  by  precipitating  the  nitrate 
or  acetate  of  lead  by  a  solution  of  chromate  or  bichromate 
of  potash.      Chrome  Green  is  the  oxyd  of  chrome,  prepared 
in  a  particular  way. 

NICKEL. 

Equivalent,  29-6.     Symbol,  Ni. 

577.  Nickel  is  rather  a  rare  metal.     It  is  prepared  from 
the  speiss  or  crude  nickel  of  commerce.     It  is  white  and 
malleable,  having  a  density  of  8  to  8 '8,  and  fuses  above 
3000°.     Reduced  from  its  oxyd  by  hydrogen  (fig.  373)  at  a 
low  temperature,  it  takes  fire  in  the  air.    The  compact  metal 
is  not  easily  oxydized.    It  is  the  only  metal  beside  iron  and 
cobalt  which  is  magnetic.  This  property  it  loses  when  heated 
to  700°.     Meteoric  iron  almost  invariably  contains  nickel, 
sometimes  as  much  as  10  per  cent.     Its  chief  ores  are  cop- 
per-nickel and  speisa-cobalt. 

Arseniuret  of  nickel  and  cobalt  is  found  at  Chatham, 
Conn.,  and  oxyd  of  cobalt  and  manganese  in  Mine-la-Motte, 
Mo.  The  emerald  nickel,  a  beautiful  green  hydrous  car- 
bonate described  by  the  author,  is  found  in  Lancaster  Co., 
Pa.  Its  formula  is  3(NiO)C02+6HO. 

578.  There  are  two  oxyds  of  nickel.     The  protoxyd  NiO 
is  prepared  by  precipitating  a  solution  of  nickel  by  caustic 
potash  :  this  is  soluble  in  ammonia.     It  gives  a  grass-green 
hydrated  oxyd,  which,  by  heat,  loses  its  water  and  becomes 
gray.     The  oxyd  of  nickel  is  isomorphous  with  magnesia, 
and  has  been  obtained  crystallized  in  regular  octahedrons. 
The  salts  of  this  oxyd  have  a  fine  green  color,  which  they 
impart  to  their  solutions. 

The  peroxyd  of  nickel  NiOa  is  a  dull  black  powder,  of 
no  particular  interest. 

579.  The  sulphate  of  nickel  NiO.S03+7HO  is  a  finely 
crystallized  salt,  occurring  in  green  prisms,  which  lose  their 

576.  What  is  chrome  yellow?  What  chrome  green?  577.  In  what 
Btate  does  nickel  occur  in  nature  ?  Describe  its  properties.  What  of  ita 
magnetic  property  ?  578.  What  are  oxyds  ?  In  what  form  does  the  proL- 
oxyd  crystallize  ?  579.  Describe  the  sulphate  and  oxalate  of  nickel. 


340  METALLIC   ELEMENTS. 

water  of  crystallization  by  heat.     It  forms  beautiful,  well 
crystallized  double  salts,  with  the  sulphates  of  potash  and 
ammonia.     Oxalic  acid  precipitates  an  insoluble  oxalate  of 
nickel  from  the  solution  of  the  sulphate,  and  the  metallic 
nickel  is  easily  obtained  from  the  oxalate  by  heat. 

Nickel  is  chiefly  employed  in  making  German  silver,  a 
white  malleable  alloy,  composed  of  copper  100,  zinc  60,  and 
nickel  40  parts. 


COBALT. 

Equivalent,  29-5.     Symbol,  Co. 

580.  Cobalt  is  a  metal  almost  always  associated  with 
nickel,  and  closely  resembling  it  in  many  of  its  reactions. 
When  pure  it  is  a  brittle,  reddish-white  metal,  with  a  density 
of  8 '53,  and  melts  only  at  very  high  temperatures.  It  is 
nearly  as  magnetic  as  iron.  It  dissolves  with  difficulty  in 
strong  sulphuric  acid,  and  is  not  oxydized  in  air.  It  forms 
two  oxyds  every  way  analogous  to  those  of  nickel.  Its  prot- 
oxyd  is  a  grayish-pink  powder,  very  soluble  in  chlorohydric 
acid.  It  forms  pink  salts.  This  oxyd  occurs  native. 

The  chlorid  of  cobalt  CoCl  is  formed  by  dissolving  the 
oxyd  in  hydrochloric  acid.  The  solution  is  pink,  and  when 
very  dilute  may  be  used  as  a  blue  sympathetic  ink,  which 
may  be  made  green  by  mixing  a  little  chlorid  of  nickel. 
Writing  made  with  this  on  paper  is  colorless  when  cold,  but 
becomes  of  a  fine  blue  or  green  when  gently  warmed,  and 
loses  its  color  again  on  cooling. 

The  salts  of  cobalt  and  nickel  are  isomorphous  with  those 
of  magnesia.  They  are  not  thrown  down  by  sulphuretted 
hydrogen,  but  give  blue  or  green  precipitates  with  potash, 
soda,  and  their  carbonates.  The  same  precipitates  with 
ammonia  are  soluble  in  excess  of  that  reagent.  Oxyd  of 
cobalt  imparts  a  splendid  blue  to  glass,  and  the  pulverized 
glass  of  this  color  is  called  smalt  and  powder  blue.  Zaffre 
is  an  impure  oxyd  of  cobalt,  used  to  give  the  blue  color  to 
common  earthenware. 


What  is  the  composition  of  German  silver?  580.  What  are  the  charac- 
ters of  cobalt?  What  interesting  experiment  is  mentioned  with  the 
chlorid  ?  With  what  oxyd  are  the  oxyd  of  cobalt  and  its  salts  isomor- 
phous ?  What  use  is  made  of  the  oxyd  of  cobalt  ? 


ZINC. 


341 


ZINC. 

Equivalent,  S2-.5.     Symbol,  Zn.     Density,  6-86  to  7-20. 

581.  Zinc  is  an  important  and  rather  common  metal.     It 
is  not  found  native,  but  a  peculiar  red  oxyd  of  zinc  abounds 
at  Sterling,  New  Jersey,  and  calamine  or  carbonate  of  zino 
is  found  abundantly  in  many  places.     The  ores  of  zinc  are 
reduced  by  heat  and  charcoal,  in  large  crucibles  closed  at 
top,  but    having   a  clay  tube  a   b 

descending  from  near  the  top,  as  in 
fig.  376,  through  the  crucible  and  its 
support  B,  to  a  vessel  of  water  C. 
The  cover  is  luted  on  and  the  heat 
raised.  The  metal,  being  volatile, 
rises  in  vapor,  which  descending 
through  the  tube,  is  condensed  in 
the  water  below.  This  is  called 
distillation  per  descensinn. 

582.  Zinc  is  a  bluish-white  metal, 
easily  oxydized  in  the  air,  and  crys- 
tallizes  in  broad   foliated  laminae, 

TjV  Q'Tft 

well  seen  in  the  fracture  of  an  ingot 

of  the  commercial  metal.  It  is  called  spelter  in  the  arts, 
and  is  largely  used  to  alloy  copper  in  forming  brass,  to  form 
sheet  zinc,  and  also  for  the  protection  of  iron  in  what  is  called 
galvanized  iron.  Zinc  is  not  a  malleable  metal  at  ordinary 
temperatures,  but  at  a  temperature  of  between  250°  and  300° 
it  becomes  quite  malleable,  and  is  then  rolled  into  sheet 
zinc.  At  about  390°  it  is  again  quite  brittle,  and  may  be 
granulated  by  blows  of  the  hammer :  at  773°  it  melts,  and 
if  air  has  access  to  it,  it  takes  fire,  and  burns  rapidly  with  a 
brilliant  whitish-green  flame,  giving  off  flakes  of  white  oxyd 
of  zinc,  anciently  called  lana  philosophica  and  pompTiolix. 
It  is  completely  volatile  at  a  red  heat.  We  constantly  em- 
ploy zinc  in  the  laboratory  to  procure  hydrogen,  and  granu- 
late it  by  turning  it  slowly  into  cold  water  from  some  height. 
It  dissolves  in  solutions  of  soda  and  of  potassa,  with  evolu- 
tion of  hydrogen  and  formation  of  zincate  of  the  alkali 
employed. 

583.  The  oxyd  of  zinc  ZnO  is  formed  when  zinc  burns 


581.  Hew  is  zinc  reduced  from  its  ores?     How  distilled ?     582.  What 
are  its  properties  ?     At  what  temperature  is  it  malleable  ? 


342  METALLIC    ELEMENTS. 

in  air.  Only  one  oxyd  is  known.  It  is,  when  pure,  a  white 
powder;  yellowish  while  hot.  It  contains  zinc  80-26,  oxygen 
19-74.  It  is  insoluble  in  water,  but  forms  a  hydrate  with  it. 
The  anhydrous  oxyd  mingled  with  drying-  oils  forms  a  valu- 
able paint,  now  coming  into  use  in  place  of  white-lead.  It 
has  the  advantage  of  not  changing  by  sulphuretted  hydro- 
gen and  of  not  being  deleterious  to  the  health  of  the  work- 
men. It  is  now  largely  manufactured  from  the  red  zinc  of 
New  Jersey,  and  from  the  franklinite  of  the  same  region, 
which  contains  a  large  quantity  of  zinc. 

Calaminc  is  a  native  carbonate  of  zinc  ZnO.C03,  and 
is  its  most  valuable  ore.  Electric  calcimine  is  a  silicate 
3(ZnO)Si08+HHO. 

Chloric?  of  zinc  ZnCl  is  a  valuable  escarotic,  and  has 
been  much  used  in  dilute  solution  to  preserve  anatomical 
subjects  for  dissection. 

Sulphuret  of  zinc,  Blende,  ZnS,  is  one  of  the  mostcommon  of 
the  ores  of  zinc.  It  occurs  in  beautiful  brilliant  crystals,  modi- 
fications of  the  first  system,  called  by  the  miners  Hack-jack. 

Sulphate  of  Zinc,  or  White  Vitriol,  ZnO.S03+7HO.— 
This  salt  has  the  same  form  as  the  sulphate  of  magnesia,  and 
looks  extremely  like  it.  It  dissolves  in  2£  parts  of  cold 
water,  at  60°,  but  at  212°  is  indefinitely  soluble,  as  it  then 
fuses  in  its  own  crystallization  water.  It  forms  double 
salts  with  the  sulphates  of  ammonia  and  potash.  It  is  a 
powerful  and  very  rapid  emetic. 

Sulphuret  of  ammonia  throws  down  a  characteristic  white 
precipitate  of  sulphuretted  zinc  from  its  neutral  solutions 

CADMIUM. 

Equivalent,  56.  Symbol,  Cd.  Density,  8'7. 
584.  Cadmium  is  generally  found  associated  with  zinc. 
It  is  quite  malleable,  white,  and  harder  than  tin.  It  fuses 
at  442°,  and  volatilizes  completely  at  a  temperature  a  little 
above  this.  It  is  not  easily  oxydized,  and  is  but  slightly 
soluble  in  chlorohydric  or  sulphuric  acid.  Nitric  acid  dis- 
solves it  with  ease,  forming  a  salt  from  which  sulphuretted 
hydrogen  throws  down  a  very  characteristic  orange-yellow 
sulphuret.  This  compound  is  also  found  native  and  crys- 
tallized, 


583.  Describe  the  oxyd  ZnO.  What  large  use  is  being  made  of  it? 
What  is  calamine  ?  Blende  ?  Sulphate  of  zinc  ?  What  of  its  solubility  ? 
584.  What  are  the  properties  of  cadmium  ? 


LEAD.  343 

Its  oxyd  CdO  is  a  bronze  powder,  formed  by  igniting  tho 
nitrate  or  carbonate,  and  rises  in  a  brown  vapor  when  cad- 
mium is  placed  in  the  focus  of  the  oxyhydrogen  blowpipe. 

LEAD. 

Equivalent,  103-5.     Symbol,  Pb.     Density,  1145. 

585.  This  useful  and  familiar  metal  occurs  in  boundless 
profusion  in  this  country.  Its  chief  ore  is  galena,  or  sul- 
phuret  of  lead,  from  which  the  metal  is  easily  obtained  by 
smelting  with  a  limited  amount  of  fuel  at  a  low  heat.  The 
carbonate,  phosphate,  chromate,  and  arseniate  are  also  na- 
tural salts  of  lead,  much  prized  by  the  mineralogist. 

Lead  is  a  bluish-gray  metal,  very  soft  and  ductile,  but  not 
very  tenacious,  (471 ;)  it  oxydizes  in  the  air  quite  rapidly, 
forming  a  coat  of  oxyd,  or  carbonate,  which  usually  protects 
it  from  further  corrosion.  Its  destiny  is  11-45,  and  it  fuses 
at  about  630°;  when  melted  it  combines  rapidly  with  oxygen 
from  the  air,  forming  either  protoxyd,  or  red  oxyd,  accord- 
ing to  the  degree  of  heat  employed.  It  is  somewhat  volatile 
above  a  red  heat. 

Lead  is  acted  upon  by  distilled  water  and  by  rain  water. 
Water,  by  reason  of  its  affinity  for  the  oxyd  of  lead,  acts 
like  an  acid  upon  metallic  lead.  A  bright  slip  of  pure  lead 
is  tarnished  almost  immediately  in  pure  water,  and  after  a 
short  time  becomes  covered  with  a  pellicle  of  carbonate  of 
lead ;  while  the  water  yields  a  dark  cloud  to  sulphuretted 
hydrogen,  showing  the  presence  of  oxyd  of  lead  dissolved  in 
it.  It  is,  therefore,  unsafe  to  use  water-pipes  of  lead,  unless 
it  has  been  proved  by  experiment  that  the  particular  water 
in  question  does  not  act  on  this  metal.  The  carbonate,  which 
is  the  salt  generally  produced  under  these  circumstances,  is 
an  energetic  poison.  The  presence  of  a  very  small  quantity 
of  foreign  mattej*  in  water,  and  especially  of  the  sulphate  of 
lime,  usually  arrests  this  action,  and  renders  the  use  of  lead- 
pipes  in  a  majority  of  cases  not  hazardous. 

Lead  does  not  easily  dissolve  in  strong  acids,  except  in 
nitric,  with  which  it  forms  a  soluble  salt :  strong  sulphuric 
acid  dissolves  it  only  when  heated,  forming  nearly  insoluble 
sulphate  of  lead. 

585.  What  is  the  chief  ore  of  lead  ?  What  are  the  properties  of  lead  ? 
Its  density  and  fusion  point?  Is  it  volatile  ?  What  acts  on  lead  ?  What 
salt  of  lead  is  most  poisonous  ?  What  arrests  the  action  of  water  on  1<^ .*  • 


344  METALLIC   ELEMENTS. 

Th  >re  are  three  oxyds  of  lead,  viz.  suboxyd  Pb30,  prot- 
oxyd  PbO,  and  peroxyd,  or  plumbic  oxyd  Pb02. 

586.  Protoxyd  of  Lead,  Litharge,  Massicot,  PbO. — This 
oxyd  is  a  yellow  powder,  formed  by  slowly  oxydizing  lead 
with  heat.  It  is  slightly  soluble  in  water,  and  the  solution 
is  alkaline  :  in  solution  of  sugar  it  is  largely  soluble.  It 
fuses  easily,  and  dissolves  silica  with  great  rapidity ;  hence  its 
use  in  glazing  pottery  (555)  and  in  the  manufacture  of  glass, 
(553.)  It  forms  a  large  class  of  definite  salts,  which  have 
often  a  sweet  takte,  as  is  seen  in  the  acetate,  or  sugar  of  lead. 
The  peroxyd  Pb03  is  prepared  by  acting  on  the  red-lead 
with  dilute  cold  nitric  acid  :  it  is  a  puce-colored  body,  which 
plays  the  part  of  an  acid,  forming  salts  with  bases.  The 
oxyd  of  lead  forms  insoluble  salts  with  the  fatty  acids,  of 
which  the  well-known  diachylon  plaster  is  an  example. 
There  are  several  intermediate  oxyds  of  lead,  called  miniums 
which  are  of  variable  composition,  according  to  the  tempera- 
ture at  which  they  are  prepared.  Red-lead  is  a  familiar  ex- 
ample of  these.  Its  formula  is  Pb304  or  2PbO.Pb02.  It 
has  a  fine  orange-red  color  when  well  prepared,  and  is  some- 
times found  crystallized  in  the  fissures  of  the  furnaces.  It 
is  prepared  by  exposing  lead  to  a  constant  temperature  of 
about  700°.  Acted  on  by  hydrochloric  acid,  it  evolves 
chlorine,  and,  with  sulphuric  acid,  oxygen  is  given  off.  It 
is  preferred  to  litharge  for  glass-making. 

The  chlorid  and  iodid  of  lead  possess  no  particular  inte- 
rest ;  the  latter  crystallizes  in  beautiful  yellow  scales  from 
its  solution  in  hot  water.  The  chlorid,  iodid, 
and  sulphate  are  all  very  insoluble  compounds. 
Sulphuretted  hydrogen  throws  down  a  black 
sulphuret  from  all  soluble  salts  of  lead,  being 
the  best  test  of  its  presence. 

587.  Zinc  precipitates  it  from  its  solutions  by 
voltaic  action,  in  beautiful  crystalline  plates  of 
metallic  lead,  which  assume  a  branching  form, 
often  an  inch  or  two  in  length,  and  hence  called 
the  lead-tree,  or  arbor  saturni,  from  the  alche- 
mistic  nallle  of  this  metal.  The  acetate  is  usually 
employed  :  an  ounce  of  the  salt  is  dissolved  in  two  quarts  of 

What  oxyds  of  lead  are  there  ?  586.  What  names  has  PbO  ?  Give 
its  properties.  What  is  PbOa?  What  is  diachylon  piaster?  What  are 
the  miniums?  What  use  is  made  of  minium?  What  test  LB  named  for 
lead  salts  ?  587.  How  is  metallic  lead  precipitated  from  its  solution  ? 


COPPER.  345 

distilled  water,  and  a  piece  of  clean  zinc  suspended  in  it  by 
a  thread :  the  precipitation  is  gradual,  and  occupies  one  or 
two  days.  The  arrangement  is  seen  in  the  fig.  377. 

588.  Carbonate  of  Lead,  White-lead,  Ceruse,  PbO.C03. 
— This  salt  is  found  beautifully  crystallized  in  nature,  but 
is  prepared  artificially  in  very  large  quantities,  for  the  pur- 
poses of  a  paint.     This  pigment  is  obtained  by  casting  lead 
in  very  thin  sheets,  which  are  then  rolled  up  into  a  loose 
Bcroll  Z  (fig.  378)  and  placed  in  a  pot  over  a  small  quantity 
of  vinegar  u,  supported  on  the  ledge  b  b,  so 

as  not  to  project  above  the  pot,  nor  touch  the 
vinegar.  The  vinegar  is  obtained  from  the 
fermentation  of  potatos.  Many  thousands  of 
these  pots  are  arranged  in  successive  layers 
over  each  other,  with  covers  n'  m  between,  and 
the  interstices  filled  with  spent  tan,  or  ferment- 
ing stable-dung,  which  gives  a  gentle  heat  to 
the  acid.  After  a  time  the  lead  is  completely  Ig'  ' 
converted  into  an  opake  white  crust  of  carbonate.  The  theory 
of  this  process  will  be  explained  when  we  describe  the  ace- 
tates of  lead,  (Organic  Chemistry.)  White-lead  is  now  largely 
adulterated  by  sulphate  of  baryta,  but  the  fraud  may  be 
easily  detected  by  dissolving  the  carbonate  in  an  acid,  when 
the  sulphate  of  baryta  will  be  left  behind.  Carbonate  of 
lead  is  highly  poisonous. 

589.  URANIUM, (equivalent  60.) — This  rare  metal  is  found 
only  in  a  few  very  rare  minerals,  of  which  the  best  known  are 
pitch  blende,  an  impure  oxyd  of  uranium,  and  uranite,  one 
of  the  most  beautiful  of  mineral  species,  which  is  a  phos- 
phate of  uranium.     The  metal  is  of  a  silver  color,  a  little 
malleable,  and  has  so  great  an  affinity  for  oxygen  as  to  burn 
in  the  air.     It  forms  two  oxyds,  UO  and  U203.     The  salts 
of  uranium  possess  considerable  chemical  interest. 

COPPER. 

Equivalent,  31-7.      Symbol,  Cu.     Density,  8-87. 

590.  Copper  has  been  in  familiar  use  since  the  times  of 
Tubal  Cain,  and  is  one  of  the  most  important  metals  to  the 

588.  How  is  the  carbonate  prepared,  and  for  what  is  it  used  ?  589.  In 
what  minerals  is  uranium  found?  What  oxyd  does  it  form?  590.  What 
is  the  history  of  copper  ? 


346  METALLIC   ELEMENTS. 

wants  of  society.  It  is  often  found  in  the  metallic  state. 
The  metallic  copper  of  Lake  Superior  is  found  in  irregular 
veins,  filling  fissures,  from  which  it  is  cut  by  chisels,  and  by 
drills  in  huge  blocks  of  great  purity.  Small  masses  of 
silver  are  also  often  found  adherent  to  the  copper.  One 
mass  from  this  region,  now  at  Washington,  weighs  over  3000 
pounds,  and  such  masses  are  frequent.  The  most  usual 
ores  of  copper  are  the  red  oxyd  of  copper,  copper  pyrites, 
and  copper  glance,  a  pure  sulphuret,  or  sulphuret  of  copper 
and  iron. 

The  blue  and  green  malachites,  or  carbonates  of  copper, 
phosphate  and  arseniate  of  copper,  and  many  other  salts  of 
this  metal,  are  also  found  in  the  mineral  kingdom.  Copper 
is  very  malleable,  and  is  the  only  red  metal  except  titanium. 
It  fuses  at  1996°,  and  has  a  density  of  8-78,  which  may 
be  increased  to  8-96  by  hammering.  It  does  not  change  in 
dry  air,  but  in  moist  air  becomes  covered  with  a  green  coat 
of  carbonate,  known  as  verdigris,  (corruption  of  the  French 
vert  de  gris.)  It  is  stiffened  by  hammering  or  rolling,  and 
softened  again  by  heating  and  quenching  in  water.  It  may 
be  drawn  into  very  fine  wire  of  good  tenacity,  which  is  an 
excellent  conductor  of  heat  and  electricity,  and  is  much 
used  in  electro-magnetism  and  for  the  telegraphic  conductors. 

Nitric  acid  is  the  proper  solvent  of  copper,  sulphuric  and 
hydrochloric  acids  scarcely  acting  upon  it. 

591.  There  are  four  oxyds  of  copper,  suboxyd  CuaO, 
protoxyd  CuO,  binoxyd  Cu03,  and  an  acid  oxyd  whose 
composition  is  unknown. 

The  protoxyd,  or  black  oxyd  of  copper,  CuO,  is  the 
base  of  all  the  blue  and  green  salts  of  copper.  It  is 
formed  by  decomposing  the  nitrate  with  heat.  It  is  black 
and  very  dense,  quite  soluble  in  acids,  and  forms  many 
important  salts  which  are  isomorphous  with  those  of  mag- 
nesia. It  yields  all  its  oxygen  to  organic  matters  at  a  red 
heat,  and  for  this  purpose  is  much  used  in  their  analysis. 

The  suboxyd,  or  red  oxyd  of  copper,  Cu30,  is  found 
native  in  beautiful  octahedral  crystals,  and  is  also  formed 
when  copper  is  oxydized  by  heat.  This  oxyd  communicates 


How  found  at  Lake  Superior  ?  What  copper  ores  are  named  ?  Give 
its  equivalent  and  characters.  What  is  the  solvent  of  copper?  591. 
What  oxyds  of  copper  are  known  ?  What  relative  to  the  black  oxyd 
of  copper  ?  Describe  the  suboxyd. 


COPPER. 


347 


to  glass  a  magnificent  ruby-red  color.     The  chlorids  and 
iodids  of  copper  are  of  no  great  importance. 

592.  Sulphate  of  copper,  blue  vitriol,  CuO.S03-f-5HO, 
is  an  important  salt,  crystallizing  in  large,  beautiful  blue 
rhombs,  which  are  soluble  in  four  parts  of  cold  and  two 
parts  of  hot  water.     It  loses  its  water  by  a  gentle  heat  and 
falls  to  a  white  powder.     It  is  much  used  in  dyeing  and  for 
exciting  galvanic  batteries.     With  ammonia  it  forms  a  dark- 
blue  crystallizable  compound. 

593.  Nitrate  of  copper  CuO.N05-f-3HO  is  formed  by 
dissolving  copper  in  nitric  acid  to  saturation,  and  is  a  deep- 
blue,  crystallizable,  deliquescent  salt,  very  corrosive,  and 
easily  decomposed  :  a  paper  moistened  with  a  strong  solu- 
tion of  this  salt  cannot  be  rapidly  dried  without  taking  fire, 
from  the  decomposition  of  nitric  acid.      The  residues  of 
operations  for  obtaining  deutoxyd  of  nitrogen  (341)  afford 
an  abundant  supply  of  this  salt  in  the  laboratory. 

Ammonia  detects  the  smallest  traces  of  this  metal  in 
solution,  by  the  deep  violet-blue  of  the  ammoniacal  salt  of 
copper  which  is  formed.  Iron  precipitates  it  from  its  acid 
solution  as  a  brilliant  red  coating.  Copper  is  a  metal  most 
readily  obtained  in  a  metallic  form  from  its  solutions  by 
voltaic  decomposition.  The  sulphate  is  usually  employed  for 
this  purpose  in  the  electro- 
type, the  arrangement  be 
ing  made  like  fig.  379,  the 
operation  of  which  has 
been  already  explained  in 
section  234.  The  alloys 
of  copper  are  much  prized 
for  their  various  useful 
applications  in  the  arts. 
Brass  is  zinc  £,  copper  f . 
Dutch  metal,  of  which  thin 
leaves  are  made,  contains  Fig.  379. 

10  to  14  of  zinc. 


592.  Describe  the  sulphate  of  copper.  593.  What  is  the  nitrate  ?  How 
does  it  affect  organic  matter?  How  is  copper  detected?  Why  is  cop- 
per used  in  electrotyping  ?  What  of  its  alloys  ? 


848  METALLIC   ELEMENTS. 


CLASS  V.  METALS  WHOSE  OXYDS  ARE  WEAK  BASES 
OR  ACIDS. 

594.  The  five  first  metals  in  this  class  are  so  rare  that 
we  may  pass  them  with  a  very  brief  mention.  They  are 

VANADIUM,       TUNGSTEN,      COLUMBIUM,     TITANIUM,      and 
MOLYBDENUM. 

Vanadium  appears  to  be  closely  allied  to  chromium. 
The  vanadic  acid  V03  forn^s  salts  with  lead  and  copper, 
found  native  as  vanadinite,  and  volborthite  CuO.V03. 

Tungsten ,  so  named  from  its  great  weight,  (12*11,)  exists 
as  tungstic  acid  W03  in  wolfram  and  scheeletine  CaO.W03 
or  tungstate  of  lime.  Native  tungstic  acid  has  been  observed 
in  Monroe,  Conn. :  it  is  a  yellow  powder,  soluble  in  ammo- 
nia, but  insoluble  in  acids. 

Columbium,  or  tantalum,  is  the  metal  of  a  mineral  called 
columbitc,  (in  allusion  to  its  American  origin,  by  Hatchett, 
its  discoverer,)  or  tantalite,  a  salt  of  iron  in  which  this  metal 
is  the  acid.  It  forms  two  oxyds,  Ta03  and  Ta03,  both  acids. 
It  is  with  the  columbite  of  Haddam  that  the  two  new 
metals,  pelopium  and  niobium,  are  found,  as  described  by 
Rose. 

Titanium  is  a  copper-red  metal,  crystallizing  in  cubes. 
It  forms  with  oxygen  titanic  acid  Ti02,  a  substance  found 
pure  in  three  distinct  minerals,  viz.  rutile,  anatase,  and 
Brookite,  an  interesting  case  of  trimorphism.  This  acid  is 
soluble  in  strong  chlorohydric  acid,  but  precipitates,  on  di- 
lution and  boiling,  a  white,  insoluble  powder,  much  resem- 
bling silica.  It  is  used  to  give  a  yellowish  tint  to  porcelain 
in  preparing  artificial  teeth. 

Molybdenum  is  a  white,  slightly  malleable,  infusible  metal, 
density  8-6.  The  sulpliuret  is  a  common  mineral  distributed 
in  primitive  rocks:  it  resembles  graphite.  It  forms  with 
oxygen  oxyd  of  molybdenum  MoO,  binoxyd  Mo03,  and  mo- 
lybdic  acid  Mo03,  which  is  its  most  important  compound. 
Molybdic  acid  forms  soluble  salts  with  the  alkalies,  of  which 
the  molybdate  of  ammonia  is  the  most  valuable,  being  the 

594.  What  is  vanadium  ?  What  is  tungsten  ?  In  what  minerals  found  ? 
What  is  colurnbiurn?  In  what  mineral  found?  What  new  metals  have 
been  found  with  it?  What  is  titanium?  What  is  titanic  acid?  What 
natural  forms  has  it?  How  is  molybdenum  found  in  nature?  What  im- 
portant salt  does  it  form  ? 


TIN.  349 

most  delicate  test  known  for  phosphoric  acid.  Molybdate  of 
lead  is  a  beautiful  native  salt  of  this  acid.  Heat  converts 
the  sulphuret  into  the  impure  acid,  and  it  is  also  oxydized 
directly  by  monohydrated  nitric  acid. 

TIN.  ( 

Equivalent,  59.     Symbol,  Sn,  (Stnanum.*)     Density,  7 -29. 

595.  Tin  is  one  of  those  metals  which  have  been  known 
from  the  most  remote  antiquity.     The  mines  of  Cornwall 
have  been  worked  for  the  oxyd  of  tin  since  the  times  of  the 
Phoenicians  and  Greeks.     It  has  been  found  in  this  country 
only  at  Jackson,  N.  H.,  in  small  quantities.     Tin  is  a  white 
metal  with  a  brilliant  lustre,  not  easily  tarnished,  and  resist- 
ing the  action  of  acids  to  a  remarkable  degree.     It  is  soft, 
very  ductile,  laminable,  malleable,  but  of  feeble  tenacity. 
Tin  foil  is  made  of  one-thousandth  of  an  inch  in  thickness, 
or  even  much  thinner.     A  bar  of  tin  when  bent  gives  a  pe- 
culiar crackling  sound,  familiarly  called  the  cry  of  tin,  due 
to  the  disturbance  of  its  crystalline  structure.     It  is  one 
of  the  best  conductors  of  heat  and  electricity. 

596.  Tin  has  a  density  of  7*29,  and  fuses  at  442°.     Its 
alloys  are  very  valuable ;  gun-metal  (copper  90,  tin  10)  is 
one  of  the  strongest  alloys  known,  of  a  reddish-yellow;  bell- 
metal  (copper  78,  tin  22)  is  a  very  sonorous  and  brittle 
alloy,  of  a  pale  yellow ',  and  speculum-metal  (copper  70  to 
75,  and  tin  25  to  30)  is  a  hard,  brilliant,  almost  white,  aad  ex- 
cessively brittle  alloy.    Pewter  is  a  mixture  of  tin  and  anti- 
mony or  lead.      Tin-plate  is  only  sheet-iron  coated  with  tin. 

Chlorohydric  acid  dissolves  tin  with  escape  of  hydrogen, 
forming  SnCl. 

Strong  nitric  acid  does  not  dissolve  tin,  but  the  addition 
of  a  little  water  to  the  acid  causes  a  violent  action,  and  the 
tin  is  speedily  converted  to  stannic  acid  Sn03. 

597.  There  are  two  oxyds  of  tin  :  1.  The  protoxyd  SnO; 
and  2.  The  peroxyd  Sn02.  There  are  numerous  intermediate 
oxyds  formed  of  these  two.     1.  This  is  obtained  by  preci- 
pitating a  solution  of  protochlorid  of  tin  with  an  alkaline 

595.  What  history  is  given  of  tin  ?  What  are  its  equivalent  and  genera* 
properties?  596.  Give  its  density  and  fusibility?  What  is  said  of  its 
alloys  with  copper?  What  is  tin-plate  and  pewter?  How  does  nitric 
acid  affect  it  ?  597.  What  oxyds  of  tin  are  there  ?  What  is  the  nrot- 
oxyd. 


350  METALLIC   ELEMENTS. 

carbonate,  which  yields  a  bulky  hydrate  ot  the  protoxyd 
It  is  a  very  unstable  compound,  passing  into  the  peroxyd  at 
a  very  moderate  heat.  2.  The  peroxyd  is  found  native  in 
the  beautiful  crystallized  tin  stone.  It  may  be  obtained  in 
a  soluble  and  an  insoluble  condition.  When  the  perchlorid 
is  precipitated  by  an  alkali,  the  bulky  white  precipitate  of 
hydrated  peroxyd  which  appears  is  easily  soluble  in  acids; 
but  if  tin  is  acted  on  by  an  excess  of  moderately  strong 
nitric  acid,  a  white  insoluble  powder  is  formed,  which  is 
not  acted  on  by  the  strongest  acids.  Heat  converts  both 
into  a  lemon-yellow  powder,  which  dissolves  in  alkalies,  but 
not  in  acids,  and  which  is  known  as  stannic  acid :  it  reddens 
test-paper,  and  forms  salts.  The  putty  used  to  polish  stone 
and  glass  is  the  peroxyd  of  tin 

598.  Protochlorid  of  tin   SnCl  which   is  prepared  by 
dissolving  tin  in  hot  chlorohydric  acid,  is  a  powerful  de- 
oxydizing  agent,  and  reduces  the  salts  of  silver,  mercury, 
platinum,  &c.,  to  the  metallic  state.     The  anhydrous  proto- 
chlorid  is  formed  by  heating  protochlorid  of  mercury  with 
powdered  tin. 

599.  Perchlorid  of  tin  SnCl3  is  a  dense  fuming  liquid, 
long  known  as  the  fuming  liquor  of  Labavius.    It  is  formed 
by  distilling  a  mixture  of  1  part  of  powdered  tin  and  5  of 
corrosive  sublimate.     The  tin  mordant  used  by  the  dyers  is 
formed  by  dissolving  tin  in  chlorohydric  acid,  with  a  little 
nitric  acid,  at  a  low  temperature,  or  by  passing  chlorine  gas 
through  the  protochlorid. 

The  sulphurets  of  tin  correspond  to  the  chlorids.  The 
bisulphuret  (aurum  musivum)  is  used  as  a  bronze  color  for 
imitating  gold  in  ornamental  painting  and  printing,  and  also 
to  excite  electricity  in  the  electrical  machine,  (166.) 

The  alchemistic  name  for  this  metal  was  Jove,  and  the 
medicinal  preparations  of  tin  are  still  called  jovial  prepa- 
rations. 

BISMUTH. 

Equivalent,  208.     Symbol,  Bi.     Density,  9-8. 

600.  Bismuthia  found  native,  and  also  in  combination  with 

Describe  the  peroxyd.  What  two  modifications  of  it  are  named  ?  How 
does  heat  affect  them?  What  is  "putty?"  598.  How  is  protochlorid  of 
tin  employed  as  a  reagent?  599.  What  is  perchlorid  of  tin,  and  how 
prepared  ?  What  is  the  tin  mordant  ?  What  sulphurets  of  tin  are  there  ? 
What  was  its  alchemistic  name  ? 


BISMUTH.  551 

other  substances.  Native  bismuth  is  found  in  the  United 
States,  at  Monroe,  Conn.  It  is  a  brittle,  highly  crystalline 
metal,  of  a  reddish-white  color,  with  a  density  of  9-8,  and 
fuses  at  507°.  It  is  obtained  in  large  and  beautiful  obtuse 
.rhombic  crystals,  by  fusing  several  pounds  of  bismuth  in  an 
earthen  pot,  purifying  by  successive  portions  of  nitre,  and 
leaving  it  to  cool  until  a  crust  is  formed  on  its  surface, 
which  is  pierced  by  a  hot  coal  and  the  still  fluid  interior 
turned  out.  The  vessel  will  be  lined  with  a  multitude  of 
brilliant  crystals. 

It  dissolves  in  nitric  acid,  but,  like  other  metals  of  this 
class,  does  not  decompose  water  under  any  circumstances. 

601.  Two  oxyds  of  bismuth  are  known.     The  protoxyd 
Bi03  is  formed  by  gently  igniting  the  subnitrate.     It  is  a 
yellowish  powder,  easily  soluble  in  acids,  and  is  the  base  of 
all  the  salts  of  bismuth.     It  is,  however,  a  very  feeble  base, 
since  even  water  decomposes  its  salts.     The  peroxyd  Bi05 
is  not  of  much  interest. 

602.  The  nitrate  of  bismuth  Bi03.N05-f  3HO  is  the  most 
interesting  of  its  salts.     It  may  be  obtained  from  a  strong 
solution  in  large  transparent  crystals,  which  are  decomposed 
by  water.     The  solution  of  the  nitrate  of  bismuth  turned 
into  a  large  quantity  of  water  is  immediately  decomposed, 
with  the  production  of  a  copious  white  precipitate  of  subni- 
trate of  bismuth.    This  is  owing  to  the  superior  basic  power 
of  the  water,  which  takes  a  part  of  the  nitric  acid.     The 
white  precipitate  is  a  basic  nitrate  Bi03.N05-f-3Bi03HO. 
This  white  oxyd  has  been  much  used  as  a  cosmetic.     It 
blackens  by  sulphuretted  hydrogen. 

603.  The  alloy  of  bismuth,  known  as  Newton's  fusible 
metal,  is  formed  of  8  parts  bismuth,  5  parts  lead,  and  3  parts 
tin,  and  melts  at  about  208°,  (473.)     It  is  much  used  in 
taking  casts  of  medals.     An  alloy  of  1  lead,  1  tin,  and  2 
bismuth,  fuses  at  200°-75.     The  expansion  of  bismuth  in 
cooling  renders  it  a  valuable  constituent  of  alloys  where 
sharpness  of  impression  in  casting  is  important. 


600.  What  is  the  color  and  fusibility  of  bismuth  ?  Describe  its  crys- 
tals, and  the  mode  of  obtaining  them.  601.  How  many  oxyds  has  this 
metal?  602.  What  is  the  most  interesting  property  of  the  nitrate  ?  What 
use  is  made  of  the  subnirate?  603.  What  its  the  composition  of  Newton'fc 
fusible  metal  ?  What  more  fusible  alloy  is  named  ? 


(552  METALLIC   ELEMENTS. 


ANTIMONY. 
Equivalent,  129.     Symbol,  Sb,  (Stibium.'}    Density,  67. 

604.  This  metal  is  derived  chiefly  from  its  native  sul- 
phuret,  which  is  a  rather  abundant  mineral.     The  metal  is 
obtained  by  fusing  the  sulphuret  with  iron-filings,  or  car- 
bonate of  potash,  which  combine  with  the  sulphur  and  set 
free  the  metal.     It  is  a  white,  brilliant  metal  with  a  blue 
tint,  forming  broad  rhomboidal  crystalline  plates  in  the  com- 
mercial article,  but  fine   granular  if  purified  from  foreign 
metals,  which  cause  it  to  assume  a  coarse  crystallization. 
It  is  very  brittle,  and,  like  bismuth,  may  be  reduced  to  a  fine 
powder.     It  fuses  at  about  842°,  and  lower  if  quite  pure  : 
a  high  fusion  point  is  a  sign  of  its  impurity.     It  is,  in  a  cur- 
rent of  hydrogen,  entirely  volatile,  but  alone  and   covered 
very  slightly  so.     It  dissolves  in  hot  chlorohydric  acid,  but 
nitric  acid  converts  it  into  the  insoluble  white  antimonic 
acid. 

Its  alloy  with  lead  is  type-metal,  which,  like  the  alloys 
of  bismuth,  gives  very  sharp  casts,  by  reason  of  the  expan- 
sion it  undergoes  at  the  moment  of  solidification,  which 
forces  the  metal  into  all  the  fine  lines  of  the  mould.  It  is 
remarkable  that  both  of  the  constituent  metals  shrink  when 
cast  separately.  Finely  powdered  antimony  is  inflamed  in, 
chlorine  gas,  forming  the  percblorid. 

605.  Two  oxyds  of  antimony  are  known,  viz : 

1.  Antimonic  Oxyd,  Sb03. — This  oxyd  may  be  obtained 
by  digesting  the  precipitate  from  chlorid  of  antimony  by 
water,  with  carbonate  of  potash  or  soda,  or  by  burning  anti- 
mony in  a  red-hot  crucible;  and  also  by  subliming  it  from 
the  surface  of  fused  antimony  in  a  current  of  air.  It  is 
a  fawn-colored  insoluble  powder,  anhydrous,  and  volatile 
when  highly  heated  in  a  close  vessel.  Boiled  with  cream 
of  tartar,  (acid  tartrate  of  potash,)  it  forms  the  well-known 
tartar  emetic,  which  may  be  obtained  in  crystals  from  the 
solution. 

The  glass  of  antimony  is  an  impure  fused  oxyd,  pre- 


604.  How  is  antimony  obtained  ?  What  are  its  properties?  What  of 
it?  grain?  Its  fusion?  Its  alloys?  C05.  How  many  compounds  does 
antimony  form  with  oxygen  ?  What  important  salt  does  the  oxyd  form 
wit)  ?otash? 


ANTIMONY.  353 

pared  for  the  purpose  of  making  tartar  emetic.  Heated 
iu  air,  this  oxyd  gains  another  equivalent  of  oxygen,  and 
forms — 

2.  Antimonic  acid  Sb05  is  formed,  as  already  stated, 
when  antimony  is  digested  in  an  excess  of  strong  nitric  acid, 
or  better  in  aqua-regia  with  nitric  acid  in  excess.  It 
dissolves  in  alkalies,  with  which  it  forms  definite  salts,  that 
are  again  decomposed  by  acids,  hydrate  of  antimonic  acid 
being  thrown  down.  The  hydrate  loses  its  water  below  a 
red  heat,  becoming  a  crystalline  fawn-colored  powder;  and 
by  a  higher  heat  one  equivalent  of  oxygen  is  expelled,  anti- 
monious  acid  being  formed. 

606.  There  are  chlorids  and  sulplmrets  of  antimony  cor- 
responding to  the  oxyd  and  to  antimonic  acid. 

The  terchlorid,  butter  of  antimony,  SbCl3,  is  made  by 
distilling  the  residue  of  the  solution  of  sulphuret  of  anti- 
mony in  strong  hydrochloric  acid,  (fig.  317.)  When  a  drop 
of  the  distilled  liquid  forms  a  copious  white  precipitate  on 
falling  into  water,  the  receiver  is  changed,  and  the  pure 
chlorid  is  collected.  It  is  a  highly  corrosive  fuming  fluid, 
and  by  cooling  forms  a  crystalline  deliquescent  solid.  It  is 
used  in  medicine  as  a  caustic.  Water  decomposes  it,  but  it 
dissolves  in  hydrochloric  acid  unchanged :  water  poured 
into  the  solution  throws  down  a  bulky  precipitate,  which  is 
a  mixture  of  oxyd  and  chlorid  of  antimony,  and  has  long 
been  known  by  the  name  of  powder  of  algaroth,  SbCl3. 
2Sb03. 

The  bromid  of  antimony  is  a  crystalline  volatile  com- 
pound. 

607.  The  tersulphuret  of  antimony  SbS3  constitutes  the 
common  commercial  sulphuret,  and  the  beautiful  crystal- 
lized native  mineral,  antimony  glance. 

The  pentasulphuret  of  antimony  SbS5  is  formed  by  boil- 
ing the  tersulphuret  with  potash  and  sulphur,  and  throwing 
down  the  compound  in  question  by  an  acid,  as  a  golden  yel- 
low sulphuret,  known  by  the  name  of  sulphur  auratumt 
or  golden  sulphur  of  antimony.  More  generally,  however, 
the  decomposition  on  adding  an  acid,  as  above,  gives  us 
the  oxysulphuret  of  antimony  SbS3-|-Sb03,  which  is  a 

What  is  antimonic  acid?  606.  Describe  the  terchlorid?  How  de- 
decomposed  ?  607.  What  is  said  of  the  sulphurets  ?  What  are  the  golden 
sulphuret  and  kermes  mineral  ? 


354  METALLIC   ELEMENTS. 

characteristic  reddish-orange  precipitate.  This  is  the  sub- 
stance known  as  Jcermes  mineral,  and  is  an  article  of  the 
older  medical  practice.  The  solution  of  sulphuret  of  anti- 
mony in  caustic  potash  and  sulphur  is  a  case  in  which 
eulphuret  of  potassium  is  a  sulphur  base,  and  sulphuret  of 
antimony  a  sulphur  acid. 

The  formation  of  tartar  emetic  with  tartaric  acid,  and 
the  production  of  the  characteristic  reddish-yellow  sulphu- 
ret of  antimony  with  sulphydric  acid  are  the  most  signal 
tests  of  antimony.  The  sulphydrate  of  ammonia  produces 
the  same  colored  precipitate,  but  this  is  soluble  in  excess  of 
the  precipitant,  as  the  former  also  is  in  the  solution  of  al- 
kalies. The  blowpipe  also  furnishes  good  evidence :  when 
a  bit  of  metallic  antimony  is  fused  under  the  oxyhydrogen 
blowpipe  it  volatilizes  and  burns,  and  if  it  be  thrown  on 
the  floor  or  an  inclined  board,  it  scatters  in  numerous  burning 
globules,  whose  path  is  marked  by  a  white  stain  of  oxyd 
of  antimony.  We  will,  under  arsenic,  mention  how  anti- 
mony is  to  be  distinguished  in  cases  of  poisoning. 


ARSENIC. 
Equivalent)  75.     Symbol,  As.     Density,  5*8. 

608.  Metallic  arsenic  is  found  native  in  thick  crusts, 
called  testaceous  arsenic,  evidently  deposited  by  sublimation. 
It  is,  however,  more  usually  obtained  in  the  form  of  arseni- 
ous  acid  As03,  from  roasting  the  ores  of  cobalt,  nickel,  and 
iron,  with  which  metals  it  is  often  combined.  Mispickel,  a 
double  sulphuret  of  iron  and  arsenic,  is  a  great  source  for 
this  metal.  The  vapors  of  arsenious  acid  given  out  in  the 
roasting  are  condensed  in  a  long  horizontal  chimney,  or  in 
a  dome  constructed  for  the  purpose ;  the  first  product  being 
purified  by  a  second  sublimation.  Arsenic  is  a  brilliant 
crystalline  steel-gray  metal,  brittle,  and  easily  pulverized. 
In  vessels  free  from  air  it  may  be  sublimed  unchanged  at  a 
temperature  of  dull  redness.  Its  vapor  is  colorless,  very 
dense,  (10-37,)  and  has  a  remarkable  odor,  resembling  garlic. 
The  garlic  odor  is  well  perceived  on  subliming  a  fragment  of 


What  is  the  nature  of  this  salt?  What  are  the  best  tests  of  antimony? 
How  does  it  act  under  the  blowpipe?  608.  How  is  arsenic  found,  and 
in  what  minerals?  What  are  its  properties?  How  is  it  sublimed  un- 
changed? What  is  the  density  and  odor  of  its  vapor? 


ARSENIC.  355 

arsenio  or  of  arsenious  acid  from  a  live  coal.  It  sublimes 
without  fusion.  It  may,  however,  be  fused  in  tight  vessels 
under  pressure  of  its  own  vapor.  Metallic  arsenic  soon 
tarnishes  in  air  and  assumes  a  dull  cast-iron  look. 
It  is  sold  by  druggists  under  the  absurd  names  of 
fly-powder,  cobalt,  and  mercury — names  intended 
to  deceive  and  likely  to  mislead,  involving  obvious 
danger.  Metallic  arsenic  is  easily  obtained  in  distinct 
crystals  by  subliming  the  commercial  metal,  or 
arsenious  acid,  mingled  with  charcoal  and  carbonate 
of  soda,  or  black  flux,  (484,)  in  a  tube  of  hard  glass, 
or,  if  a  larger  quantity  is  required,  in  a  small  retort. 
The  mixture  is  put  in  a  b,  (fig.  380,)  and  heated  to 
redness  while  the  air  is  shut  out.  The  metal  rises 
and  is  deposited  in  a  black  metallic  mirror  in  the  cool 
part  of  the  tube  just  above.  Metallic  arsenic  is  an 
active  poison.  It  burns  in  the  air  with  a  blue 
flame,  and  it  is  also  inflamed  in  chlorine  gas.  Fis-  38°- 

609.  The  oxyds  of  arsenic  are,  1.  Arsenious  acid  As03, 
and  2.  Arsenic  acid  As05. 

1.  Arsenious  Acid — White  Arsenic — Ra£s-l>ane,  As03j 
— This  well-known  and  fearful  poison  is  formed,  as  just 
stated,  when  metallic  arsenic  is  sublimed  in  air,  or  when 
any  of  the  ores  of  arsenic  are  roasted.  This  oxyd  is  what  is 
usually  meant  when  the  term  arsenic  is  used  in  commerce. 
When  newly  sublimed,  it  is  a  hard  transparent  glass,  brittle, 
and  with  a  density  of  3*7.  It  slowly  changes  to  a  white 
opake  enamel,  resembling  porcelain.  This  change  is  gradual, 
the  vitreous  portions  being  still  found  in  the  centre  of  the 
opake  masses.  As  sold  in  commerce,  it  is  usually  reduced 
to  a  white  powder,  rarely  found  without  adulteration.  It 
sublimes  at  380°,  without  change,  and  crystallizes  in  bril- 
liant octahedrons,  as  may  be  well  seen  by  slowly  subliming 
a  small  quantity  in  a  glass  tube.  Its  vapor  is  inodorous, 
but  if  sublimed  from  charcoal  it  gives  the  peculiar  garlic 
odor  of  metallic  arsenic,  being  reduced  to  that  state.  It  is 
soluble  in  about  10  parts  of  hot  water,  and  is  almost  taste- 
less, with  a  faint  sweetish  flavor,  which  renders  it  the  more 

How  may  it  be  fused?  How  does  air  affect  it?  What  names  has  it? 
How  obtained  crystallized?  609.  What  oxyds  does  it  form?  Give  formu- 
las. What  is  arsenious  acid?  What  are  its  common  names  ?  What  are 
its  characters  ?  What  change  does  it  suffer  ?  How  does  it  crystallize  ?  How 
soluble  ?  What  of  its  taste  ? 


356  METALLIC   ELEMENTS. 

dangerous  poison,  since  no  warning  is  given  to  the  victim 
who  takes  it,  as  in  case  of  most  other  metallic  poisons.  The 
vitreous  acid  is  three  times  as  soluble  as  the  opake.  The 
solution  in  water  is  acid  to  test-paper,  and  deposits  nearly 
all  its  arsenic  in  crystals  on  cooling,  retaining  1  part 
to  30  of  water.  Chlorohydric  acid  dissolves  arsenic,  and 
if  a  solution  of  4  parts  As03  in  6  of  HC1  and  2  of  water 
is  slowly  cooled  from  boiling,  the  As03  is  deposited  in  trans- 
parent octahedrons,  and  if  in  the  dark,  the  formation  of  each 
crystal  is  accompanied  by  a  spark,  and  sometimes  the  light 
produced  is  such  as  to  illuminate  a  dark  room.  The  alka- 
lies dissolve  arsenic,  but  do  not  form  crystallizable  salts  with 
it.  Arsenious  acid  contains  As  75-75,  0  24-25. 

610.  Arsenic  Acid,  As05. — This  acid  is  formed  by  adding 
nitric  acid  to  the  solution  of  white  arsenic  in  hydrochloric 
acid,  as  long  as  any  red  vapors  of  nitrous  acid  show  them- 
selves, and  then  carefully  evaporating  the  solution  to  entire 
dryness  :  a  white  porous  subcrystalline  mass  remains,  which 
is  slowly  soluble  in  water.     Its  solution  is  a  powerful  acid, 
quite  similar  in  chemical  characters  to  phosphoric  acid.    The 
analogy  is  so  great  that  there  is  a  complete  similarity  in  con- 
stitution, and  even  in  external  appearance,  between  all  the 
salts  of  these  two  acids.     For  every  tribasic  phosphate  we 
have  an  arseniate,  not  only  similar  in  constitution,  but  iso- 
morphous,  and  so  resembling  it  in  all  its  external  properties 
as  not  to  be  distinguished  by  the  eye.     Thus  the  tribasic 
phosphate  of  soda  (512)  and  the  tribasic  arseniate  of  soda, 
are — 

Phosphate  of  soda H02NaO.POl-f-24Aq. 

Arseniate  of  soda H02NaO.AsO»-f-24Aq. 

These,  and  many  other  facts,  lead  to  the  opinion  that  the 
elements  are  themselves  isomorphous;  and  in  fact  arsenic  has 
no  claim  to  the  metallic  character  but  its  lustre,  being  in 
chemical  properties  and  natural  affinities  associated  with 
phosphorus. 

611.  The  clilorid  of  arsenic  AsCl3  is  a  fuming  volatile 
liquid,   decomposed  by  water,   and  very   poisonous.      The 
bromid  and  iodid  are  both  crystallizable  solids,  also  decom- 
posed by  water. 

What  is  said  of  its  chlorohydric  solution  ?  610.  How  is  AsO»  formed? 
What  are  its  properties?  What  analogy  has  it  with  P0§?  To  what 
opinion  do  these  facts  lead  ?  611.  What  of  chlorid  of  arsenic  ? 


ARSENIC.  357 

The  sulphurets  of  arsenic  are  natural  compounds,  used  as 
pigments,  and  also  in  pyrotechny.  The  first,  AsS2,  is  a  red 
transparent  body,  called  realgar,  and  AsS2  is  the  golden- 
yellow  orpiment.  Both  these  substances  are  found  native^ 
and  are  usually  associated.  They  are  brought  from  Koor- 
distan  in  Persia,  and  from  China.  The  Mohammedans  use 
the  yellow  orpiment  as  a  depilatory  in  their  ceremonial  puri- 
fications. Two  higher  sulphurets  may  be  formed,  which  are 
AsOs  and  As09 :  the  former  is  the  product  thrown  down 
by  sulphuretted  hydrogen  in  a  solution  of  arsenic.  The 
sulphurets  are  soluble  in  alkalies  and  in  sulphydrate  of  am- 
monia. 

612.  Arseniuretted  Hydrogen,  AsH3. — This  is  a  gas  pro- 
duced by  the  action  of  dilute  sulphuric  acid  on  an  alloy  of 
zinc  and  arsenic,  or  by  the  evolution  of  hydrogen  in  presence 
of  arsenic  or  arsenious  acid. 
Figure  381  shows  the  ordinary 
gas  evolution  bottle  A,  in  which 
are  the  materials  for  producing 
hydrogen.  An  arsenical  solution 
poured  in  at  n  m,  immediately 
changes  the  color  of  the  flame 
at  6;  before  colorless,  it  now 
becomes  of  a  peculiar  blue,  and 
evolves  a  cloud  of  arsenious  acid,  Fig.  381. 

or  deposits  metallic  arsenic  on  a  cold  surface.  Marsh's  test 
for  arsenic  depends  on  the  generation  of  this  gas.  It  is  a 
virulent  poison  of  the  most  active  description.  This  gas  is 
readily  absorbed  by  a  solution  of  sulphate  of  copper,  and 
precipitates  an  arseniuret  of  that  metal.  Its  density  is  2-69 : 
it  has  a  peculiar  disgusting  odor,  and  is  decomposed  by  heat 
alone  with  deposition  of  metallic  arsenic.  It  is  liquid  at 
— 22°F. :  water  dissolves  it  slightly,  and  chlorine  completely 
decomposes  it  with-  flame. 

Detection  of  Arsenic  in  Poisoning. 

613.  The  too  frequent  use  of  arsenic  as  a  means  of  destroy- 
ing human  life  renders  it  of  the  greatest  moment  to  know 
certain  processes  for  its  detection.  Arsenic  is  almost  always 

What  are  the  sulphurets  ?  612.  What  is  arseniuretted  hydrogen  ?  How 
produced?  What  of  its  flame?  What  are  its  properties?  613.  What 
of  arsenical  poisoning  ? 


S58  METALLIC    ELEMENTS. 

fatal  when  it  lias  time  to  become  absorbed  by  the  circulation 
in  sufficient  quantity.  The  most  reliable  antidotes  which 
have  been  proposed  are  the  moist  hydrates  of  sesquioxyd 
of  iron  and  of  caustic  magnesia.  With  both  these  arsenic 
forms  insoluble  salts.  The  alkalies,  being  solvents  of  arsenic, 
only  increase  the  danger  by  favoring  absorption. 

We  enumerate  a  few  of  the  tests  for  arsenious  and  arsenic 
acids : 

1.  Sulphydric  acid  produces  in  acid  or  neutral  solutions 
of  As03  and  As05  a  rich  orange-yellow  precipitate,  (orpi- 
ment,)  soluble  in  ammonia  and  alkalies,  and  in  sulphydrate 
of  ammonia,  but  precipitated  again  by  acids. 

2.  Nitrate  of  silver  and  ammonia-nitrate  of  silver  pro- 
duce in  solutions  of  arsenious  acid  a  lemon-yellow  precipitate, 
(arsenite  of  silver,)  soluble  in  nitric  acid.     In  solutions  of 
arsenic  acid  they  produce  a  brick-red  precipitate. 

3.  Ammonia-sulphate  of  copper  gives  a  brilliant  green 
precipitate  (Sdieelds  green)  in  alkaline  or  neutral  solutions  of 
arsenious  acid,  which  precipitate  (arsenite  of  copper)  is  soluble 
in  excess  of  ammonia. 

4.  A  slip  of  Iriyht  metallic  copper,  placed  in  a  boiling 
solution  of  arsenic  or  arsenious  acid  made  acid  by  chloro- 
hydric  acid,  is  soon  coated  with  a  gray  deposit    of  metallic 
arsenic.     This  is  called  Reinsch's  test,  and  is  applicable  even 
in  presence  of  organic  matters  which   vitiate,  partially  or 
wholly,  the  previous  tests. 

5.  Reduction  of  the  metal  from  the  oxyds  or  sulphurets 
is  justly  esteemed  in  judicial  investigations  as  the  most  reli- 
able of  all-  tests.     This  is  accomplished  by  several  modes. 

The  oxyds  or  sulphurets  are  min- 
gled  with  finely-powdered  charcoal 
and  carbonate  of  soda  or  cyanid 


$T^  of  potassium  and  placed  in  a  small 

tube  a  d  (fig.  382)  of  hard  glass. 
The  part  a   b  is  heated  red   hot, 
FlS-  3S2«  when,  if  arsenic  is  present,  it  is 

sublimed  in  a  black  metallic  mirror  at  c.     A  small  tube  is 
used,  because  in  many  cases  very  minute  portions  are  ope- 


What  are  antidotes,  and  why  ?  How  does  sulpbydric  acid  act  as  a  test 
of  arsenic  ?  How  nitrate  of  silver  and  ammonia  ?  How  ammonia-sul- 
phate of  copper?  What  is  Reinsch's  test?  What  of  the  reduction  pre- 
ferred? Describe  from  fig.  382. 


ARSENIC. 


859 


Fig.  383. 


rated  on.     In  order  to  prove  the  character  of  this  ring,  the 

tube  is  broken  off  at  b,  (fig.  383,)  and  the 

flame  of  a  spirit-lamp  applied  cautiously 

while  the  tube  is  gently  inclined.     A 

current  of  air  passing  over  the  ring  of 

metal  converts  it  to  arsenious  acid,  which 

lines  the  cooler  parts  of  the  tube  with 

email   brilliant    octahedrons   of  a   size 

visible  by  a  magnifier.     If  further  proof 

were  required,  a  current  of  sulphydric 

acid  will  convert  the  white  crust   into   yellow  orpiment, 

wholly  soluble  in  ammonia,   precipitated  by  chlorohydric 

acid,  and  insoluble  in  that  menstruum. 

6.  Marsh's  test,  by  means  of  arseniuretted  hydrogen,  gives 
unequivocal  testimony  when  arsenic  is  present.  Fig.  384 
shows  a  convenient  form  of  the  apparatus  used 
for  this  purpose,  which  is  more  simply  arranged 
as  in  fig.  381.  This  apparatus  has  the  conve- 
nience of  a  cock  to  regulate  the  escape  of  the 
gas.  The  zinc  is  in  the  lower  bulb — the  acid 
water  and  suspected  substance  are  introduced 
by  the  upper  bulb.  The  zinc  and  all  the 
materials  employed  must  be  scrupulously  ex- 
amined as  to  freedom  from  arsenic.  For  this 
purpose  the  flame  of  hydrogen  muse  not  give  the 
least  spot  upon  clean  porcelain.  On  adding 
the  arsenical  solution,  however,  the  flame  be- 
comes livid,  larger,  gives  off  white  vapors,  and 
deposits  a  tache  or  spot,  in  the  form  of  brown-  Flg>  384> 
black  mirror,  on  the  surface  of  porcelain,  as  in  fig.  385. 
Antimony  gives  a  similar  spot,  which  is  liable  to  be  con- 
founded with  that  from  arsenic.  It  is,  however,  more  sooty- 
black.  Exposed  to  vapor  of  iodine  in  a  small  capsule,  anti- 
mony spots  turn  reddish  orange,  while  arsenic  spots  appear 
orange  yellow,  and  soon  vanish  entirely.  Exposed  for  a 
moment  to  vapor  of  chlorine  given  off  from  bleaching-pow- 
ders  in  a  capsule,  the  spots  being  on  the  underside  of  the 
cover  of  the  same,  the  spots  disappear.  If  a  drop  of  nitrate 
of  silver  be  then  let  fall  on  the  flat  surface,  if  arsenic  was 

How  is  itoxydizedin  fig.  383  ?  What  further  proof  may  be  had?  What 
is  Marsh's  test  ?  Describe  fig.  384.  What  care  is  required  ?  What  eft'ect 
is  seen  on  introducing  an  arsenic  solution  ?  What  gives  a  similar  spot  ? 
How  are  the  spots  distinguished  ?  How  by  chlorine  and  nitrate  of  silver  ? 


360  METALLIC   ELEMENTS. 

present  there  will  be  a  brick-red  stain  visible,  amounting  to 
a  precipitate  if  much  of  the  metal  existed — while  antimony 
does  no  such  thing.  These  distinctions  are  conclusive. 

The  arrangement  of  Marsh's  apparatus  recommended  by 
the  commission  of  the  Paris  Academy,  in  cases  of  judicial 
investigation,  is  shown  in  fig.  385.  The  evolution  bottle  A 


Fig.  385. 

is  provided  with  a  bulb-tube  a  I,  to  retain  moisture,  which  is 
more  effectually  removed  by  the  chlorid  of  calcium  tube  c  d. 
The  gas  is  conducted  through  the  horizontal  tube  f  y,  ter- 
minating in  a  jet-point,  where  the  taclie  of  the  flame  can  be 
received  upon  a  clean  porcelain  surface  C.  As  heat  decom- 
poses the  arseniuretted  hydrogen,  means  are  provided  to 
heat  the  tube  while  the  gas  is  passing,  the  radiant  heat 
being  cut  off  by  a  screen  c.  In  this  case  the  metallic  arsenic 
appears  in  a  ring  at  /,  while  the  flame  loses  its  peculiar 
character,  and  no  taclie  is  seen  at  y.  The  ring  so  obtained 
may  be  subsequently  tested  as  before  indicated,  as  well  also 
as  the  tache.  The  cause  of  the  tache  will  appear  on  a 
moment's  attention.  Calling  to  mind  what  was  said  on  the 
structure  of  flame,  (460,)  it  is  obvious,  by  reference  to  fig. 

386,  showing  a  larger  view 
of  the  jet  <7,  (fig.  385,)  that 
.  the  part  d  c'  must  contain 
'  the  reduced  arsenic  in  hot 
hydrogen  gas,  surrounded 
by  the  burning  envelope 
a  c  I.    Now  the  porcelain 
Pig- 386'  surface  is  held  in  the  line 


Des'cribe  fig.  385.    What  does  the  heat  accomplish  ?    How  is  the  tache 
•btained  in  fig.  385  ? 


MERCURY.  361 

z  x,  and  must  receive  the  metallic  mirror,  if  any  arsenic  is 
present. 

614.  In  most  cases  of  arsenical  poisoning  it  is  required 
to  search  for  proof  in  the  mass  of  organic  matters  ejected  by 
the  patient,  or  in  the  tissues  of  the  body  itself;  and  either 
case  requires  all  organic  matters  to  be  destroyed  before  tests 
can  be  applied.     This  may  be  done  in  a  great  majority  of 
cases  by  oxydizing  and  charring  the  whole  mass  to  be  treated, 
cut  small,  in  a  porcelain  capsule,  with  a  mixture  of  strong 
nitric  acid  and  oil  of  vitriol.     These  are  added  in  small 
quantity,  and  gentle  heat  applied  until  the  coaly  mass  is  nearly 
dry.    Water  is  then  added,  and  the  whole  thrown  upon  a  filter 
and  washed  :  the  filtrate  contains  all  the  arsenic  and  other 
metals.     Marsh's,  Reinsch's,  or  any  of  the  other  tests  just 
enumerated  may  then  be  applied.     Such  is  a  very  brief  ac- 
count of  the  most  valuable  modes  of  examination  in  cases  of 
poisoning   by  arsenic.     Further  details  would  be   out  of 
place  here. 

CLASS  IV.  NOBLE  METALS:  WHOSE  OXYDS  ARE  RE- 
DUCED BY  HEAT  ALONE. 

MERCURY. 

Equivalent,  100.      Symbol,  Hg,  (Hydrargyrum?)     Density, 
13-596. 

615.  This  is  the  only  metal  which  is  fluid  at  ordinary 
temperatures.    It  is  found  as  native,  or  running  mercury,  in 
Spain  and  Carniola,  and  also  as  cinnabar,  or  sulphuret  of 
mercury.    In  Upper  California  a  very  large  deposite  of  cin- 
nabar has  lately  been  opened.    It  is  also  found  both  in  Mexico 
and  Peru.     The  alchemists  supposed  it  to  be  silver  enchant- 
ed, (quicksilver,*)  and  made  many  efforts  to  obtain  from  it 
the  solid  silver  it  was  supposed  to  contain. 

Pure  mercury  is*  a  silver-white,  fluid  metal,  unchanged  by 
air,  and  very  brilliant.  Cooled  below — 3944°,  as  by  car- 
bonic acid,  (150,)  it  solidifies,  and  is  then  as  malleable  as 
lead.  It  crystallizes  in  cubes.  It  boils  at  662°,  and  forms 
a  colorless  vapor,  of  the  density  6-976.  Even  at  32°,  a 


614.  How  is  proof  obtained  in  case  of  organic  matters  being  present? 
What  agent  of  oxydation  is  used?  How  is  the  testing  carried  on  ?  What 
are  noble  metals?  615.  What  of  mercury?  How  found?  Why  called 
quicksilver  ?  What  arc  its  properties  ? 


362  METALLIC   ELEMENTS. 

very  rare  vapor  rises  from  it,  as  is  evident  from  the  effect 
on  claguerrian  plates.  If  heated  in  the  air  at  or  above  600°, 
it  slowly  passes  to  the  condition  of  red  oxyd  of  mercury, 
which  is  its  highest  combination  with  oxygen.  By  this  ex- 
periment Lavoisier  proved  the  composition  of  air,  and  per- 
formed the  first  recorded  chemical  analysis. 

616.  The  uses  of  mercury  are  numerous  and  important  in 
the  arts,  and  also  in  medicine.     It  forms  alloys  (amalgams) 
with  many  other  metals  ;  with  tin  it  constitutes  the  brilliant 
coating  of  glass  mirrors,  (called  silvering,)  and  it  is  of  indis- 
pensable importance  in  procuring  gold  and  silver  from  their 
ores,  and  in  gilding  by  the  old  process.     Its  use  in  filling 
thermometers  and  barometers  has  already  been  noticed.     It 
expands  by  each  degree  of  Fahr.  37^  of  its  bulk,  in  heat- 
ing from  32°  to  212°,  and  at  nearly  the  same  ratio  for  the 
whole  scale  of  662°. 

617.  The  purity  of  mercury  is  roughly  judged  of  by  its 
forming  no  film  on  glass,  and  by  its  breaking  into  small 
globules,  which  should  preserve  their  spherical  form,  when 
they  run  from  an  inclined  surface.    If  they  form  a  queue,  or 
drag  a  tail,  as  the  workmen  express  it,  it  is  owing  to  the 
presence  of  lead  or  some  other  similar  impurity. 

It  may  be  purified  from  all  non-volatile  ingredients  by 


Fig.  387. 

distillation  in  an  iron  bottle  A,  (fig.  387,)  formed  of  one  of 
the  iron  flasks  in  which  quicksilver  is  imported.     This  is 

What  of  its  volatility?  616.  What  are  its  uses?  What  fits  it  spe- 
cially for  thermometers  ?  What  is  its  rate  of  expansion  ?  617.  How  it 
its  purity  judged  of?  How  is  it  purified  ?  Describe  fig.  387. 


MERCURY.  363 

completely  enclosed  in  the  furnace,  and  the  tube  5  c  con- 
nects with  a  bag  of  leather  or  caoutchouc,  reaching  to  a  basin 
of  water,  and  kept  cool  by  a  stream  of  water  from  the  cock 
r.  The  tension  of  its  vapor  is  very  small,  so  that  it  quickly 
returns  to  the  fluid  state,  thus  producing  a  great  commotion 
in  the  process  of  boiling.  The  distilled  mercury  is  only 
partly  purified,  and  the  process  must  be  completed  by  the 
action  of  dilute  nitric  acid  at  a  gentle  heat,  which  unites  to 
form  nitrate  of  mercury  with  a  part  of  the  mercury.  This 
salt  reacts  with  the  other  portion  of  the  mercury  to  form 
nitrates  of  all  other  metals  which  may  be  present.  After  a 
day  or  two,  with  frequent  agitation,  the  action  is  complete, 
the  water  is  evaporated  at  a  gentle  heat,  and  the  crust  of 
nitrate  of  mercury  removed.  The  remaining  mercury,  now 
quite  pure,  is  washed  with  much  water  and  dried. 

Mercury  may  be  so  finely  divided  by  agitation  and  other 
mechanical  means,  as  to  lose  its  metallic  appearance  entirely, 
as  in  blue  pill,  mercurialized  chalk,  (creta  cum  hydrargyrof) 
and  mercurial  ointment,  which  do  not,  as  has  sometimes 
been  stated,  contain  the  suboxyd  of  mercury,  but  only 
mercury  in  a  state  of  very  minute  mechanical  division. 

Nitric  acid  dissolves  mercury  very  rapidly  even  in  the 
cold :  hydrochloric  acid  scarcely  acts  on  it,  and  sulphuric 
only  by  the  aid  of  heat,  when  it  forms  an  insoluble  sul- 
phate of  mercury,  evolving  sulphurous  acid.  The  equiva- 
lent of  mercury  is  often  stated  at  200,  on  the  supposition 
that  the  gray  oxyd  is  the  protoxyd ;  but  this  seems  to  be 
more  properly  considered  as  a  suboxyd,  and  the  real  pro- 
toxyd as  the  red  oxyd.  On  this  view  the  equivalent  is 
stated  at  100. 

618.  The  gray,  or  suboxyd  of  mercury,  Hg30,  is  formed 
by  digesting  calomel  in  caustic  potash,  or  by  adding  the 
same  reagent  to  a  solution  of  the  nitrate  of  the  suboxyd  of 
mercury.  It  is  an  insoluble,  dark  gray  powder,  which  is 
easily  decomposed  into  metallic  mercury  and  the  red  oxyd, 
Hg96  =  HgO+Hg. 

The  red  oxyd,  or  protoxyd,  red  precipitate,  HgO,  is 
prepared  in  the  large  way  by  heating  the  nitrate  very  cau- 
tiously until  it  is  quite  decomposed,  and  a  brilliant  red 

How  is  the  purification  completed  ?  How  does  mechanical  action  af- 
fect it?  Give  examples.  What  dissolves  it?  How  does  S03  affect  it? 
What  of  its  equivalent  ?  618.  How  is  suboxyd  formed  ?  How  decom- 
posed ?  How  is  the  red  oxyd  formed  ?  What  is  precipitate  per  se  ? 


364  METALLIC   ELEMENTS. 

crystalline  powder  produced.  It  may  also  be  formed  bj 
heating  metallic  mercury  for  a  long  time  in  a  glass  vessel 
nearly  closed,  and  in  this  form  is  the  preparation  to  which 
the  old  name  of  red  precipitate  per  se  was  applied.  Heat 
decomposes  this  oxyd,  into  oxygen  and  metallic  mercury. 
It  is,  like  the  oxyd  of  lead,  slightly  soluble  in  water,  and 
gives  to  it  an  alkaline  reaction.  It  is  a  poison,  and  is  used 
externally  as  an  irritant  and  escharotic. 

619.  The  chlorids  of  mercury  correspond  to  the  oxyds, 
and  are  both  very  important  compounds. 

1.  Subcklorid  of  Mercury,  (Calomel,)  Hg3CL— This  well- 
known  medicine  is  formed  by  precipitating  a  solution  of  sub- 
nitrate  of  mercury  with  common  salt.  A  white,  insoluble,  taste- 
less powder  falls,  which  is  the  calomel.     Even  strong  acids, 
when  cold,  do  not  affect  it ;  but  it  is  instantly  decomposed 
by  alkalies,  and  the  suboxyd  produced.      Heat  sublimes  it 
unchanged.     Its  complete  insolubility  at  once  distinguishes 
this   safe  and  mild   substance  from   the  highly  poisonous 
corrosive  sublimate.     It  should  be  in  very  tine  powder  for 
medical  use,  as  then  the  presence  of  corrosive  sublimate  is 
easily  detected  in  it  by  imparting  its  taste  to  water.     Its 
freedom  from  adulteration  may  be  determined  by  heating  it 
on  the  surface  of  a  clean  spatula,  when  it  should  volatilize 
unchanged  without  leaving  any  residue.     It  is  obtained  by 
slow  sublimation,  in  beautiful  transparent  crystals — square 
prisms  with  octahedral  summits.     Its  density  is  6-5,  and  in 
vapor  8-2.     Vapor  of  calomel  is  composed  of 

1  volume  of  mercury  vapor 64976 

i  volume  of  chlorine 1*220 

1  volume  of  calomel  vapor..  HgaCl 8'196 

Calomel  is  decomposed  by  nitric  acid,  forming  corrosive 
sublimate  and  nitrate  of  protoxyd  of  mercury.  Ammonia 
turns  it  to  a  gray  powder,  which  is  an  amid  and  chlorid  of 
mercury  Hg?Cl.HgNH3. 

2.  Corrosive  Sublimate,  or   Chlorid  of  Mercury,  HgCl. 
— This  salt  is  most  economically  prepared  by  the  decompo- 
sition  of   sulphate    of   mercury,  by  common    salt,   whose 

How  does  heat  affect  it?  How  is  it  used?  619.  What  of  the  chlo- 
rids? What  is  the  name  of  the  subchlorid  ?  How  formed  ?  What  are  its 
properties  ?  What  of  its  state  and  purity  ?  Its  density  ?  What  is  the 
constitution  of  its  vapor?  What  decomposes  it?  What  is  corrosive 
sublimate  ? 


MERCURY.  365 

simple  interchange  gives  corrosive  sublimate  and  sulphate 
of  soda,  HgO.S08+NaGl  =  HgCl-|-NaO.S08;  The  chlo* 
rid  is  also  formed  by  dissolving  the  red  precipitate  in  hot 
chlorohydric  acid.  Corrosive  sublimate  is  a  very  heavy 
crystalline  body,  soluble  in  about  16  parts  of  cold  water, 
and  in  two  or  three  parts  of  hot,  giving  a  solution  which 
possesses  the  most  distressing  and  nauseous  metallic  taste, 
and  is  a  deadly  poison.  It  is  soluble  in  alcohol  and  ether. 
It  melts  at  509°  and  sublimes  at  about  563°.  Its  vapor 
has  a  density  of  942,  and  contains 

1  volume  of  vapor  of  mercury 6-967 

1  volume  of  chlorine 2-440 

1  volume  HgCl 9-407 

Albumen  completely  precipitates  it,  and  the  whites  of 
eggs  or  milk  are  therefore  antidotes  for  this  poison.  For  the 
same  reason  it  is,  doubtless,  that  timber  and  animal  sub- 
stances are  preserved  from  decay,  as  in  the  kyanizing  pro- 
cess, by  steeping  in  solution  of  corrosive  sublimate.  The 
albuminous  portions  of  wood  suffer  decay  sooner  than  the 
vegetable  fibre,  and  these  are  rendered  completely  inde- 
structible in  the  process  of  Mr.  Kyan,  which  is  now  in  use 
in  our  national  shipyards. 

Ammonia  produces  in  solution  of  corrosive  sublimate  (and 
also  in  those  of  other  salts  of  protoxyd  of  mercury)  a 
white  bulky  precipitate  of  uncertain  composition,  and  long 
known  as  white  precipitate.  It  is  regarded  as  a  double  amid 
and  chlorid  of  mercury  Hg3Cl.NHa. 

620.  There  are  two  iodids  of  mercury,  Hg3I  and  Hgl. 
— The  second  is  a  brilliant  scarlet-red  precipitate,  formed 
by  adding  solution  of  iodid  of  potassium  or  hydriodic  acid 
to  a  solution  of  corrosive  sublimate.  The  iodid  is  at  first 
yellow,  but  soon  passes  by  molecular  change  into  the  splen- 
did scarlet  crystalline  powder  before  noticed.  It  cannot  be 
used  as  a  pigment  on  account  of  its  instability. 

Two  sulphurets  of  mercury  exist  Hg2S  and  HgS,  the  first 
of  which  is  a  black  powder,  formed  when  sulphuretted  hy- 
drogen is  passed  through  a  solution  of  subnitrate  of  mercury. 
The  sulphuret  HgS,  or  cinnabar,  is  formed  when  the  nitrate 

How  procured?  Give  the  formula.  Give  its  properties.  What  is  the 
density  of  its  vapor?  What  is  an  antidote  for  it  ?  What  is  kyanizing? 
What  is  white  precipitate  ?  620.  What  iodids  of  mercury  are  there  ? 
What  sulphurets  ? 


366  METALLIC    ELEMENTS. 

of  mercury  (nitrate  of  the  red  oxyd)  is  treated  with  sulphu- 
retted hydrogen.  It  is  a  black  precipitate,  but  turns  red 
when  sublimed,  and  forms  the  familiar  pigment,  vermillion. 
This  is  the  common  ore  of  the  quicksilver  mines. 

Salts  of  Mercury. 

621.  The  salts  of  protoxyd  of  mercury  HgO  are  colorless, 
but  the  basic  salts  are  yellow. 

The  Nitrates  of  Mercury. — The  action  of  nitric  acid  on 
mercury  varies  with  the  temperature  and  the  strength  of  the 
acid.  In  the  cold,  dilute  nitric  acid  dissolves  mercury, 
forming  a  neutral  nitrate  of  the  suboxyd ;  but  if  the  mercury 
is  in  excess,  a  salt  is  deposited  in  large  and  transparent  white 
crystals,  which  is  a  nitrate  with  excess  of  base.  If  hot  and 
strong,  the  nitrate  of  the  red  oxyd  is  formed,  which  is  a  very 
soluble  salt,  not  crystallizable.  A  basic  salt  of  this  oxyd 
may  also  be  formed,  which  is  decomposed  by  water. 

Sulphate  of  mercury  HgO.S03  results  as  an  insoluble 
white  subcrystalline  powder,  by  the  action  of  the  strong  acid 
on  metallic  mercury,  sulphurous  acid  being  evolved.  Boil- 
ing water  decomposes  this  salt,  removing  a  part  of  its  acid, 
by  which  a  yellow  basic  sulphate  is  formed,  known  as  tur- 
peth  mineral.  Its  composition  is  3HgO.S03.  The  sulphate 
of  the  gray  oxyd  HgaO.S03  is  formed  as  a  crystalline  white 
powder,  by  treating  a  solution  of  subnitrate  of  mercury  with 
sulphuric  acid.  It  is  slightly  soluble  in  water.  Fulminat- 
ing mercury  and  other  cyanids  are  described  in  the  organic 
chemistry. 

All  the  compounds  of  mercury  are  volatile  at  a  red  heat ; 
and  those  which  are  soluble  whiten  a  slip  of  clean  copper, 
by  depositing  metallic  mercury  on  its  surface. 

SILVER. 

Equivalent^  108.     Symbol,  Ag.  (Argentum.}    Density,  10-5. 

622.  The  mines  of  Mexico  and  of  the  Southern  Andes 
furnish  most  of  the  silver  of  commerce,  although  many  mines 
of  this  metal  are  found  in  Spain,  Saxony,  and  the  Hartz 
Mountains.     Galena,  or  the  native  sulphuret  of  lead,  is  also 

What  is  vermilion?  621.  How  are  the  nitrates  of  mercury  obtained? 
What  is  the  nature  of  the  nitrate  of  the  red  oxyd  ?  How  is  the  sulphate 
formed?  What  are  the  characteristics  of  mercurial  compounds?  622. 
From  what  sources  is  silver  obtained  ? 


SILVER.  367 

a  constant  source  of  silver,  as  it  is  never  quite  free  from  this 
precious  metal.  Silver  is  often  found  native.  It  is  more 
usually  in  combination  with  sulphur  and  antimony. 

The  brilliant  lustre  and  white  color  of  this  valuable  metal 
are  familiar  to  all.  It  is  perfectly  ductile  and  malleable,  and 
in  hardness  stands  between  gold  and  copper.  For  the  pur- 
poses of  economy  and  in  coinage  it  is  essential  to  alloy  it 
with  about  T^  part  of  copper,  to  render  it  sufficiently  stiff 
and  hard.  It  is  one  of  the  best  conductors  of  heat  and 
electricity,  and  its  surface  reflects  light  and  heat  more  per- 
fectly than  any  other  metal.  It  is  used  for  this  reason  in 
reflectors ;  and  hot  fluids  longer  retain  their  heat  in  vessels 
of  silver  than  in  any  other.  It  remains  untarnished  in  air  free 
from  sulphur  gases ;  from  these  it  gains  a  brown-black  sur- 
face of  sulphuret  of  silver.  It  does  not  combine  with  oxygen 
when  heated  in  it ;  but  fused  silver  absorbs  even  twenty  times 
its  volume  of  oxygen,  parting  with  it  again  on  cooling.  It 
is  slightly  volatile  even  in  the  furnace,  but  in  the  carbon 
crucible  of  the  galvanic  focus  (fig.  169)  it  volatilizes  com- 
pletely. It  crystallizes  in  cubes  often  very  beautifully 
modified.  It  fuses  at  1873°;  and,  owing  to  its  absorption 
of  oxygen  and  disposition  to  contract  in  the  mould,  it  is  a 
difficult  metal  to  cast.  Nitric  acid  dissolves  silver  in  the 
cold  with  great  rapidity,  and  if  it  contains  any  gold,  this  is 
left  undissolved  as  a  brown  powder.  Solution  of  coin  alloy 
appears  green,  from  the  copper  it  contains.  Hydrochloric 
acid  scarcely  acts  on  silver,  and  sulphuric  acid  only  when 
hot,  forming  the  sparingly  soluble  sulphate. 

Silver  is  obtained  pure  from  its  solution  in  nitric  acid  by 
precipitation  with  metallic  copper,  as  a  finely-divided  crys- 
talline powder ;  also  by  decomposing  its  chlorid  by  fusion 
with  two  parts  of  dry  carbonate  of  potash. 

623.  Silver  is  parted  from  alloys  of  copper  and  from  argen- 
tiferous lead  by  the  process  of  cupdlation.  This  depends  on 
the  oxydation  of*  the  base  metal  in  a 
current  of  heated  air,  and  the  absorption 
of  these  oxyds  by  the  cupel.  This  is 
made  of  bone-ashes,  and  compacted  in  a 
mould  into  the  form  of  fig.  388 ;  seen  in  Fig.  3SS. 

What  are  the  properties  of  silver?  What  does  fused  silver  absorb? 
How  volatile?  What  of  coin  ?  What  dissolves  it?  What  separates  me- 
tallic silver  from  its  solution?  623.  What  is  cupellatiori  ?  Describe  thy 
cupel. 


368 


METALLIC   ELEMENTS. 


section  in  fig.  389.     The  bone-ash  does  not  fuse  at  tne  most 
intense  heat  of  the  cupellation  furnace.      The 
cupels  are  of  various  sizes,  according  to  the  weight 
of  the  assay.  In  metallurgic  art  they  are  employed 
Fig.  389.     in  the  final  purification  of  silver-lead,  of  immense 
size,  constructed  on  a  hearth  of  bricks.     Those  here  figured 
are  small,  and  are  heated  in  a  muffle,  or  low  oven-shaped  ves- 
sel, (fig.  390,)  set  in  the  cupellation  furnace, 
as  shown  in  section  A,  (fig.  392.)     Several 
cupels   are    accommodated    on    its   hearth, 
Fig.  390.         while  the  air  entering  its  mouth  D,  partly 
closed  by  E,  draws  over  the  surface  of  the  fused  assay,  and 
out  at  the  lateral  slits  A  in  the  muffle,  thus  oxydizing  the 


Fig.  392. 


Fig.  391. 

lead.  Fig.  391  is  a  general  view  of  the  cupellation  furnace, 
which  is  formed  of  three  parts,  united  where  the  bands  are 
shown.  The  sectional  drawing  (fig.  392)  indicates  more 
clearly  the  relations  of  the  parts.  Small  charcoal  is  fed  to 
the  fire  Or  at  F,  and  the-  ignited  coal  finds  its  way  to  B,  where 
it  rests  on  the  hearth  E.  To  aid  this  descent,  an  iron  rod 


What  is  the  muffle?     Describe  the  process  and  figs.  391  and  392. 


SILVER.  369 

is  introduced  from  time  to  time  at  o  o,  (fig.  391.)  The 
opening  I  H  regulates  the  draft,  which  is  suspended  by  open- 
ing F  G.  The  muffle  is  thus  heated  very  intensely,  and  the 
condition  of  the  assay  is  observed  from  time  to  time  by  re- 
moving E.  M  is  the  draft-pipe,  and  N  a  sheet-iron  shelf  to 
receive  the  hot  cupels.  Pure  metallic  lead  is  usually  added 
to  the  alloy  to  be  cupelled,  to  several  times  its  weight.  The 
oxyd  of  lead  is  absorbed  as  fast  as  it  is  formed,  carrying 
with  it  oxyd  of  copper  and  other  impurities  into  the  porous 
bone-ash.  Finally,  at  the  close  of  the  process,  the  globule 
of  silver  flashes  into  a  perfectly  polished  sphere  or  button 
of  a  white  color.  This  is  one  of  the  most  ancient  and  valu- 
able of  metallurgical  operations,  and  is  equally  applicable 
to  gold  and  its  alloys  as  to  silver.  By  this  process  all  the 
currency  of  the  world  is  regulated, — in  connection  with  the 
process  of  solution  in  nitric  acid,  and  precipitation  by  a  stand- 
ard solution  of  salt,  which  is  known  as  Gay-Lussac's  wet 
assay  in  distinction  from  cupellation,  which  is  called  the  dry 
method. 

624.  Much  of  the  lead  of  commerce  contains  too  little  silver 
to  allow  an  economical  use  of  the  process  of  cupellation.    The 
silver  is  then  separated  by  Pattinson's  process,  as  it  is  called, 
founded  on  the  fact  that  the  alloy  of  silver  and  lead  is  more 
fusible  than  pure  lead;  and  the  latter,  on  cooling,  separates 
in  small  crystals,  which  can  be  skimmed  out  of  the  richer  lead 
by  an  iron  cullender.     This  process  enables  the  metallurgist 
to  remove  with  profit  even  so  small  a  proportion  as  six  ounces 
of  silver  from  a  ton  of  lead.    The  small  portion  of  rich  lead 
is  then  cupelled. 

625.  Three  oxyds  of  silver  are  known  by  chemists :  the 
suboxyd  Ag20 ;  the  protoxyd  AgO ;  and  the  peroxyd  AgOa. 
We  will  now  notice  only  the  protoxyd.     This  is  formed 
when  the  solution  of  silver  in  nitric  acid  is  saturated  with 
caustic  potash,  or  when  the  chlorid  of  silver,  recently  pre- 
cipitated, is  digested  in  a  solution  of  caustic  potash  of  den- 
sity 1-3.     It  is  a  dark-brown  or  black  powder,  if  prepared 
by  the  first  mode,  or  quite  black  and  dense  by  the  second 
process.     It  is  a  base,  forming  well-defined  salts.    Ammonia 

How  does  the  button  appear  at  the  consummation  of  the  process? 
What  is  the  wet  and  what  the  dry  assay  ?  624.  What  is  Pattinson's  pro- 
BOSS  ?  625.  What  oxyds  of  silver  are  there  ?  How  is  AgO  formed  ? 
What  are  its  properties  ? 

24 


370  METALLIC   ELEMENTS. 

dissolves  it  readily,  and  it  is  also  somewhat  soluble  in  water, 
to  which  it  gives  an  alkaline  reaction.  The  solution  of  oxyd 
of  silver  in  cyanid  of  potassium  forms  the  silver-plating  so- 
lution in  this  branch  of  electro-plating.  The  oxyd  is  easily 
reduced  by  heat  alone,  and  by  the  contact  of  organic  matter. 
626.  Chlorid  of  silver  AgCl  is  formed  when  any  soluble 
salt  of  silver  is  treated  with  a  soluble  chlorid  or  with  chlo- 
rohydric  acid.  This  substance  fuses  at  a  moderate  red 
heat  into  a  transparent  pale-yellow  fluid,  which  is  horny  and 
tough  when  solid,  and  hence  called  horn  silver,  a  form  in 
which  this  metal  is  sometimes  found  in  mines.  It  is  very 
sensitive  to  light,  turning  dark  and  finally  black,  especially 
in  contact  with  organic  matter  in  sunlight.  It  is  easily 
reduced  to  the  metallic  state  by  the  nascent  hydrogen  gene- 
rated when  zinc  is  acted  on  by  dilute  sulphuric  acid  in  con- 
tact with  the  chlorid.  Pure  silver  and  chlorid  of  zinc  result ; 
or  it  may  be  reduced  by  fusion  with  twice  its  weight  of  car- 
bonate of  soda  or  potash,  (622.) 

The  iodid  and  bromid  of  silver  are,  like  the  chlorid,  inso- 
luble in  water,  and  very  sensitive  to  light.  The  daguerreo- 
type and  calotype  are  both  dependent  on  the  sensitiveness 
of  these  compounds  to  light,  for  the  accuracy  and  beauty 
of  their  results. 

The  sulphurets  of  silver  are  found  native,  and  the  tarnish 
which  blackens  silver  articles  on  long  exposure,  is  formed 
by  sulphuretted  hydrogen  in  the  air. 

627.  The  nitrate  of  silver  AgO.N05  is  a  salt  which  crys- 
tallizes in  beautiful  flattened  tables  of  an  hexagonal  form, 
soluble  in  half  their  weight  of  hot  water.  By  heat  it  fuses, 
and,  when  cast  in  cylindrical  moulds,  forms  the  slender 
sticks  called  lunar  caustic,  so  much  used  by  the  surgeon. 
Its  solution  has  a  disgusting  metallic  taste,  even  when  very 
dilute.  It  is  a  most  delicate  test  of  the  presence  of  chlorine 
or  of  any  of  its  compounds.  It  blackens  rapidly  in  contact 
with  organic  matter  when  exposed  to  the  light,  and  forms 
an  indelible  ink,  which  is  much  used  in  marking  linen. 
Solution  of  cyanid  of  potassium  will  remove  the  stain  pro- 
duced by  nitrate  of  silver.  Metallic  copper  at  once  throws 
down  metallic  silver  from  the  nitrate,  and  solution  of  nitrate 

626.  Describe  the  chlorid.  How  can  it  be  reduced?  What  are  tho 
relations  of  the  silver  compounds  to  light?  What  is  the  action  of  sul- 
phuretted hydrogen  on  silver  ?  627.  Describe  the  nitrate.  What  is  lunar 
caustic  ?  What  are  its  reactions  ? 


GOLD.  37i 

of  copper  is  formed.  Mercury  precipitates  metallic  silver 
from  a  dilute  solution,  in  beautiful  tree-like  forms,  called 
arlor  Diance.  Ammonia,  by  acting  on  precipitated  oxyd 
of  silver,  forms  a  fulminating  compound.  It  is  extremely 
hazardous  to  deal  with,  as  it  explodes  even  when  wet. 

The  fulminating  silver  produced  by  the  reaction  of  alco- 
hol, nitric  acid,  and  silver,  will  be  described  in  the  Organic 
Chemistry. 

GOLD. 

Equivalent,  98-7.     Symbol,  Au.    Density,  19-26. 

628.  This  valuable  metal  is  found  only  in  the  metallic  or 
native  state,  being  very  widely  diffused  in  small  quantities 
in  the  older  rocks.     From  these,  by  the  action  of  various 
causes,  it  finds  its  way  into  the  sand  of  rivers,  and  is  dis- 
tributed in  small  quantities,  in  many  widespread  deposits 
of  coarse  gravel  or  shingle,  as  in  Alta  California,  Australia, 
on  the  eastern  flanks  of  the  Ural  mountains,  and  over  a  wide 
belt  of  country  in  Virginia,  the  Carolinas,  Georgia,  and  Ala- 
bama.    These  diluvial  deposits  furnish  nearly  all  the  gold 
of  commerce,  by  the  process  of  washing  and  amalgamation 
with  mercury.     Large  masses  of  gold  sometimes  occur,  as 
one  of  twenty-eight   pounds   in   North  Carolina.     In    Si- 
beria a  mass  was  found,  now  in  the  Imperial  Cabinet  of  St. 
Petersburg,  weighing  nearly  eighty  English  pounds.  Several 
of  still  greater  size,  mingled  with  quartz,  have  been  found 
in  California.     Generally,  however,  it  occurs  only  in  minute 
rounded  and  flattened  grains  or  scales.     It  is  also  found  in 
veins  of  quartz,  in  compact  limestone,  and  distributed  in 
iron  pyrites.     Native  gold  is  usually  alloyed  with  from  5 
to  15  per  cent,  of  silver.     Since  the  discovery  of  gold  in 
California,  in  March  1847,  it  is  estimated  that  at  least  fifty 
millions  of  dollars  have  been  annually  obtained  there,  chiefly 
from  the  auriferous  sands  of  those  regions. 

629.  Gold  is  distinguished  by  its  splendid  yellow  color, 
its  brilliancy,  and  freedom  from  oxidation,  by  its  extreme 
malleability  and  ductility,  by  its  high  specific  gravity,  (19-26 
to  19-5,)  and  by  its  indifference  to  nearly  all  reagents.     It 


What  is  the  arlor  Diance  ?    628.  How  does  gold  occur  in  nature  ?    How 
t&  it  obtained?    What  of  California ?     629.  Describe  this  metal  ? 


372  METALLIC  ELEMENTS. 

fuses  at  2016°  F.,  and  is  dissolved  only  by  aqua  regia, 
(420,)  chlorine,  nascent  cyanogen,  and  by  selenic  acid.  The 
first  is  the  solvent  commonly  known,  and  yields  perchlorid 
of  gold. 

630.  Gold   forms  two  very  unstable  oxyds,  Au20  and 
Au303,  which  are  decomposed  even  by  light.     Two  corre- 
sponding chlorids  exist.     The  perchlorid  is  a  very  deliques- 
cent salt,  forming  a  red  crystalline  mass,  soluble  in  ether, 
alcohol,  and  water.     Metallic  gold  is  deposited  in  elegant 
crystalline  crusts  from  the  ethereal  solution  of  the  chlorid. 
Ammonia  throws  down   from   solutions  of  gold  an  olive- 
brown  powder,  fulminating  gold,  which,  when  dry,  explodes 
with  heat,  or  by  percussion. 

631.  The  solution  of  protosulphate  of  iron  throws  down 
gold  from  its  solutions  in  a  very  fine  brown  powder,  which, 
when  diffused  in  water,  is  green,  as  seen  by  transmitted  light. 
The  protochlorid  of  tin  forms  a  characteristic  purple  preci- 
pitate in  gold  solution,  called  the  purple  of  'Cassius,  which 
is  used  in  porcelain-painting,  and  is  probably  a  compound 
of  the  oxyds  of  tin  and  gold.     Gilding  of  ornamental  work 
is  usually  performed  by  gold-leaf;   but   other  metals  are 
gilded,  either  by  applying  it  as  an  amalgam  with  mercury, 
the  mercury  being  afterward  expelled  by  heat,  or  preferably 
by  the  new  process  of  galvanic  gilding  from  a  solution  of  the 
double  cyanid  of  gold  and  potassium.      Gold  wash,  as  it  is 
called,  is  applied  by  a  mixture  of  carbonate  of  soda  or  potash 
in  excess,  with  oxyd  of  gold,  in  which  small  articles  cleansed 
in  nitric  acid  are  boiled,  and  thus  become  perfectly  covered 
with  a  very  thin  film  of  gold. 

632.  PALLADIUM,  Pd. — This  very  rare  metal  is  usually  as- 
sociated with  gold,  being  found  in  a  native  alloy  of  gold  and 
silver  from  Brazil.     It  is  a  white  metal,  more  brilliant  than 
platinum,  very  infusible,  malleable,  and  ductile.     It  is,  how- 
ever, fused  by  the  compound  blowpipe.     It  gains  a  blue 
tarnish,  like  steel,  by  heating  in  the  air,  which  it  loses  by  a 
white  heat.    In  hardness  it  is  equal  to  fine  steel,  and  it  does 
not  lose  its  elasticity  and  stiffness  by  a  red  heat.    Its  density 
varies  from  10-5  to  11-8.     It  suffers  no  change  by  exposure 

What  is  its  usual  solvent  ?  630.  How  many  oxyds  of  gold  are  there  ? 
Describe  the  perchlorid.  031.  What  tests  distinguish  gold?  How  ia 
gilding  effected  ?  632.  What  of  palladium  ?  What  peculiar  properties 
Us  it? 


PLATINUM.  373 

in  the  air.  It  gives  a  peculiar  and  beautiful  color  to  the 
surface  of  brass  when  applied  in  the  electro-metallurgical 
process.  Its  equivalent  is  53-3.  Its  qualities  would 
render  it  a  vety  valuable  metal  if  it  could  be  obtained  in  a 
sufficient  quantity.  Nitric  acid  dissolves  it  slowly,  but  aqua 
regia  more  rapidly.  It  forms  two  oxyds  and  two  correspond- 
ing chlorids. 

PLATINUM. 

Equivalent,  98-7.     Symbol,  PL     Density,  19*70  to  21-23. 

633.  Platinum  is  a  very  remarkable  metal,  and,  if  abun- 
dant, would  be  extensively  useful  in  domestic  economy.  It 
is  found  native  in  the  gold-workings  in  South  America,  and 
in  Siberia  on  the  eastern  slope  of  the  Urals.  No  ore  of 
platinum  is  known  except  its  alloy  with  gold,  and  those 
with  iridium,  osmium,  and  rhodium. 

Platinum  is  a  white  metal,  between  tin  and  steel  in  color, 
but  harder  than  gold  or  silver,  and,  unless  quite  pure,  is, 
when  unannealed,  nearly  as  hard  as  palladium.  A  very 
little  rhodium  or  iridium  renders  it  more  gray  in  color  and 
much  harder.  If  pure  it  is  very  malleable,  especially  when 
hot,  and  can  then  be  imperfectly  welded.  Its  ductility  and 
tenacity  are  remarkable  ;  but  its  most  valuable  property  is 
its  infusibility,  which  is  so  great  that  the  thinnest  platinum 
foil  may  be  safely  exposed  to  the  most  intense  heat  of  a 
wind  furnace.  It  is  soluble  only  by  aqua  regia.  It  alloys 
readily  with  lead,  iron,  and  other  base  metals,  so  that  great 
care  is  needed  in  using  platinum  vessels,  not  to  heat  them  in 
contact  with  any  metal  or  metallic  oxyd  with  which  they 
combine.  Caustic  potash,  and  phosphoric  acid,  in  contact  with 
carbon,  will  also  act  upon  platinum  at  a  red  heat.  This 
is  a  most  useful  metal  to  the  chemist,  and  vessels  of  plati- 
num are  quite  indispensable  in  the  operations  of  analysis. 
Large  retorts  or  boilers  are  made  of  it  for  the  use  of  manu- 
facturers of  sulphuric  acid,  holding  sometimes  sixty  or 
more  gallons.  In  Russia  it  has  been  employed  in  coinage, 
for  which  by  its  great  density  and  hardness  it  is  well  suited. 
When  recently  fused  by  the  compound  blowpipe  or  the  gal- 


633.    What  is  the  history  of  platinum  ?      Describe  its  characters  and 
ics  ?     What  of  its  density  ? 


374  METALLIC   ELEMENTS. 

vanic  focus,  its  density  is  about  19-9,  which  is  increased  to 
21*5  by  pressure  and  heat. 

634.  Platinum  is  obtained  pure  by  digesting  crude  plati- 

num in  aqua  regia,  and  adding  to  the  deep- 
brown  liquid  a  solution  of  chlorid  of  ammo- 
nium :  this  throws  down  an  orange-colored 
precipitate,  which  is  a  double  chlorid  of  plati- 
num and  ammonium.  This  precipitate  is 
reduced  by  heat  to  the  metallic  state, — a 
porous  dull-brown  mass,  commonly  known  as 
platinum  sponge.  All  the  platinum  of  com- 
merce is  treated  in  this  way.  The  sponge  is 
condensed  in  steel  moulds,  like  fig.  393,  by  heat 
and  pressure,  and  when  compact  enough  to  bear 
the  blows  of  the  hammer,  is  heated  and  forged 
until  it  is  perfectly  tough  and  homogeneous. 
The  follower  K  is  driven  down  by  the  hammer 
upon  the  platinum  sponge  confined  in  the  steel 
seat  c  b. 

Spongy  platinum  is  a  very  remarkable  sub- 
stance, having,  as  already  noticed,  (409,)  power 
Fig.  393.     ^0  cause  the    combination  of    hydrogen    and 
oxygen,  and  to  effect  other  chemical  changes  without  being 
itself  altered. 

Platinum  black  is  a  still  more  curious  form  of  this  metal. 
It  is  formed  by  electrolyzing  a  weak  solution  of  chlorid  of 
platinum,  when  the  black  powder  appears  on  the  negative 
electrode.  The  silver  plates  in  Smee's  battery  (192)  are 
prepared  in  this  way.  It  is  also  prepared  by  adding  an 
excess  of  carbonate  of  soda,  with  sugar,  to  a  solution  of 
chlorid  of  platinum,  and  gradually  heating  the  mixture  to 
near  212°,  stirring  it  meanwhile.  The  black  powder  which 
falls  is  afterward  collected  and  dried.  This  powder  has 
the  property  of  causing  union  among  gaseous  bodies — as, 
for  example,  the  elements  of  water — to  a  greater  degree 
than  the  spongy  platinum. 

635.  Platinum  forms  two  oxyds,  and  two  chlorids,  viz. 
P10;  P103  and  P1C1;  P1C12.    The  oxyds  are  prepared  from 
the  chlorids  by  precipitation  with  alkalies,  and  are  very 


634.  How  is  it  obtained  from  its  ores  ?  How  is  it  condensed  ?  What 
Is  platinum  black,  and  what  arc  its  properties  ?  C35.  How  is  the  bi- 
ehlorid  prepared  ? 


OSMIUM.  375 

unstable.  The  protochlorid  is  prepared  by  heating  the 
bichlorid  to  460°,  when  chlorine  is  evolved  and  P1C1  is 
left  as  a  greenish-gray  insoluble  powder. 

The  bichlorid  of  platinum  is  the  usual  soluble  form  of 
platinum,  and  is  always  formed  when  platinum  is  digested 
in  aqua  regia.  It  is  prepared  pure  by  dissolving  spongy 
platinum  in  this  menstruum,  and  cautiously  expelling  the 
acid  by  evaporation,  at  the  temperature  of  a  water-bath.  It 
gives  a  rich  orange  colored  solution  both  in  alcohol  and  water; 
and  forms  insoluble  salts  of  much  interest,  with  many  metallic 
chlorids.  Those  with  the  alkaline  metals  are  the  most  im- 
portant. The  double  chlorid  of  platinum  and  potassium  is 
a  very  sparingly  soluble  salt,  (P1C12KC1,)  which  falls  as  a 
yellow,  highly-crystalline  precipitate,  when  chlorid  of  plati- 
num is  added  to  a  solution  of  chlorid  of  potassium.  The 
double  chlorid  of  sodium  and  platinum  (PlCl3NaCl-|-6HO) 
is,  on  the  other  hand,  very  soluble,  and  forms  large  beautiful 
yellowish-red  crystals  in  a  dense  solution.  Potash  and 
soda  are  most  easily  separated,  by  the  different  solubility  of 
their  double  platino-chlorids.  The  double  chlorid  of  am- 
monium and  platinum  (P1C13NH4C1)  is  the  orange  precipi- 
tate before  named,  and  is  the  best  test  to  determine  the 
presence  of  platinum  in  a  solution. 

Associated  with  platinum  are  iridium,  osmium,  rhodium, 
and  ruthenium — metals  whose  rarity  permits  us  to  pass  them 
with  a  very  brief  mention. 

636.  IRIDIUM  (Eq.  99)  is  found  alloyed  with  osmium, 
forming  the  mineral  iridosmine,  IrOs3,  in  flat  scales,  mal- 
leable with  difficulty.  It  is  the  hardest  alloy  known, 
being  as  hard  as  quartz.  It  is  very  infusible.  It  is  true  tin- 
white,  crystallizes  in  hexagonal  forms,  and  its  density  is  from 
19 -3  to  21-12  being  the  densest  body  known.  This  mineral 
is  much  used  to  point  gold  pens.  It  is  unacted  on  by  aqua 
regia.  It  forms  four  oxyds. 

OSMIUM  (Eq.  99-6)  has  a  density  of  10,  of  a  bluish-white 
color,  is  neither  fusible  nor  volatile,  and  forms,  by  its  com- 
bustion in  air,  the  very  volatile  and  poisonous  osmic  acid 
Os4.  It  forms  five  oxyds,  OsO,  Os203,  Os20,  Os30,  and  Os40. 
Fused  with  nitre,  osmium  forms  osmiate  of  potassa. 

Describe  the  double  chlorids  of  platinum  and  the  alkalies,  their  prepa- 
tion  and  characteristics.  What  metals  are  associated  with  platinum  ? 
636.  What  of  iridiurn?  What  use  has  iridosmine?  What  is  the  density 
of  iridium?  What  of  osmium?  Its  oxyds? 


376  METALLIC   ELEMENTS. 

RHODIUM  (Eq.  52-2)  is  so  named  from  the  rose  color  of  its 
salts.  It  is  a  reddish-white  metal,  density  about  10-5,  and 
resembles  iridium  in  hardness,  fusibility,  and  malleability, 
as  well  as  in  resisting  the  action  of  acids.  It  forms  two 
oxyds,  RhO  and  Rh20r 

RUTHENIUM  (Eq.  52-2)  is  another  metal  observed,  lately, 
to  the  extent  of  5  or  6  per  cent.,  in  the  iridosmine.  Its  den- 
sity is  about  8-6.  It  is  very  like  iridium  in  all  its  charac- 
ters, and  has  until  lately  been  confounded  with  it. 

What  of  rhodium?  Its  color  and  density?  Its  oxyds?  What  o! 
rutheniu  m  ?  Where  found  ?  What  relations  has  it  ? 


877 


PART  IV.— ORGANIC  CHEMISTRY. 

[THE  last  edition  of  this  work  was  written  about  five  years  since,  and 
having  been  desired  to  prepare  this  portion  of  the  book  for  a  new  edition, 
it  was  thought  proper  to  re-write  it  almost  entirely.  The  views  of  chemical 
theory  here  adopted,  have  been  in  part  advanced  in  the  pages  of  the  "Ame- 
rican Journal  of  Science"  during  the  last  four  years.  I  have  there  at- 
tempted to  point  out  what  I  conceive  to  be  true  in  the  respective  systems 
of  Giessen  and  Montpellier;  and  have  laid  down  certain  principles,  which, 
in  the  present  work,  have  been  applied  to  the  elucidation  of  a  variety 
of  questions.  I  have  refrained  from  here  developing  at  full  length  my 
own  theoretical  views,  as  being  from  their  novelty  unsuited  to  the  cha- 
racter of  an  elementary  treatise. 

It  has  been  my  plan  to  select  from  the  great  amount  of  matter  which 
the  chemistry  of  the  carbon  series  now  embraces,  those  subjects  whose  his- 
tory is  well  known  and  best  fitted  to  illustrate  the  theory  of  the  science, 
and  at  the  same  time  to  include  the  matters  most  interesting,  in  a  practical 
view,  to  the  medical  and  general  student.  Both  these  classes  will,  how- 
ever, find  it  necessary  to  resort  to  more  extended  works  for  the  history 
of  many  series  of  compounds,  which  have  been  omitted  or  very  briefly 
noticed  in  these  pages;  while,  on  the  other  hand,  it  is  hoped  that  the  more 
advanced  student  will  not  find  the  work  unworthy  of  a  perusal. 

I  have  not  thought  it  necessary  in  an  elementary  treatise  to  cite 
authorities ;  but  I  may  remark  that  I  have  availed  myself  of  the  works 
of  Liebig,  Gerhardt,  and  Gregory,  and  of  the  various  chemical  memoirs 
which  have  appeared  in  the  different  scientific  periodicals  for  the  last  few 
years.  The  most  recent  discoveries  in  organic  chemistry  are  here  em- 
bodied. 

T.  STEBEY  HUNT. 

MONTREAL,  CANADA  EAST,  July,  1852.] 


INTRODUCTION. 
Nature  of  Organic  Bodies. 

637.  Definition. — The  name  of  Organic  Chemistry  is  used 
to  designate  that  branch  of  the  science  which  investigates  the 
phenomena  and  results  of  organic  life,  examines  the  che- 
mical relations  of  animals  and  plants,  and  the  properties  and 


378  ORGANIC    CHEMISTRY. 

transformations  of  the  peculiar  bodies  which  they  afford. 
The  constituents  of  organic  bodies  are  comparatively  few  in 
number.  Carbon  with  oxygen,  hydrogen,  and  nitrogen, 
form  all  the  combinations  peculiar  to  organic  substances. 
In  addition  to  these,  however,  sulphur,  phosphorus,  and 
iron  sometimes  occur  in  small  quantities  in  organic  products; 
and  the  results  of  their  decompositions  and  transforma- 
tions under  the  influence  of  different  reagents,  give  rise  to 
an  immense  number  of  compounds,  in  which,  with  the  four 
organic  elements  already  mentioned,  are  often  united  sul- 
phur, phosphorus,  arsenic,  antimony,  chlorine,  bromine, 
iodine,  and  the  metals. 

638.  It  was  formerly  supposed  that  the  production  of  the 
so-called  organic  substances  was  exclusively  the  prerogative 
of  life.    But  later  discoveries  have  shown  that  it  is  possible 
so  to  combine  the  organic  elements  as  to  form  many  of  the 
products  which  were  formerly  obtained  only  through  the 
medium  of  plants  and  animals.     Hence  the  distinction  be- 
tween organic  and  inorganic  chemistry  is  no  longer  so  well 
denned  as  before.    But  as  in  organic  bodies  carbon  is  always 
present,  and  is  the  only  constant  element,  we  may  define  or- 
ganic chemistry  as  the  chemistry  of  the  compounds  of  carbon. 
We  may  distinguish  in  mineral  chemistry  many  such  classes 
of  compounds;  as  the  nitrogen  series,  in  which  nitrogen  is  a 
constant  and  characteristic  element;  the  silicon  series,  in- 
cluding all  the  silicious  compounds :    so   in  studying  the 
chemistry  of  organic  bodies,  we  find  that  they  may  all  be  re- 
duced to  one,  the  carbon  series. 

639.  Among  the  organic  matters  which  make  up  the 
structure  of  living  beings,  we  must  distinguish  two  classes  : 
first,  organized  substances,  which  show  either  to  the  naked 
eye,  or  under  the  microscope,  a  peculiar  structure,  entirely 
different  from  that  of  crystallization,  and  never  exhibited 
except  in  those  matters  which  have  been  formed  under  the 
influence  of  the  vital  force:  such  are  the  woody  and  muscular 
fibres,  the  cellular  and  vascular  tissues,   the   globules   of 
blood  and  of  starch  (which  see).     These  are  not  always 
homogeneous  chemical  compounds,  and  art,  even  could  it 
imitate  their  chemical  constitution,  will  never  succeed  in 
giving  them  their  organized  forms.     The  power  which  effects 
this  must  ever  remain  one  of  the  secrets  of  life. 

The  second  class  of  organic  substances  includes  those 
which  are  either  produced  by  the  destruction  of  organized 


LAWS   OF   CHEMICAL   TRANSFORMATIONS.  379 

bodies,  or  are  the  secretions  or  excretions  of  organized 
beings.  They  are  subject  to  the  same  laws  of  form  as  in- 
organic bodies,  and  are  liquid,  solid,  or  gaseous,  crystallized 
or  amorphous.  It  is  this  second  class  of  organic  substances 
which  we  are  able  to  form  artificially,  and  which  are  pro- 
perly in  the  domain  of  the  chemist ;  among  these  are  in- 
cluded the  various  alcohols,  oils,  acids,  resins,  sugars,  gums, 
alkaloids,  and  coloring  matters. 

640.  The  immediate  effect  of  chemical  agencies  upon  or- 
ganized bodies  is  to  produce  disorganization,  and  to  convert 
them  into  substances  which  belong  to  the  second  class. 
Hence  the  study  of  organized  structures  belongs  to  the  phy- 
siologist, and  it  is  only  where  he  leaves  them  that  the 
chemist  begins.     The  effect  of  strong  heat  upon   organic 
bodies  is  peculiar.     They  are  completely  decomposed  into 
a  variety  of  products,  among  which  are  water,  carbonic  acid 
gas,  carburets  of  hydrogen,  and,  if  nitrogen  be  present,  am- 
monia.    The  carbon,  which  is  generally  present  in  larger 
quantity  than  is  required  to  form  these  compounds,  remains 
in  the  form  of  charcoal;  hence  organic  bodies  are  always 
more  or  less  combustible,  and,  unless  volatile,. generally  char 
or  blacken  by  heat. 

641.  In  addition  to  the  bodies  of  the  carbon  series,  both 
animals  and  vegetables  contain  salts  of  potash,  soda,  lime, 
magnesia,  and  iron,  with  sulphuric,  phosphoric,  and  silicic 
acids,  chlorine  and  fluorine.     Animals  also  secrete  phosphate 
and  carbonate  of  lime  to  form  their  bones,  as  in  vertebrates, 
and  their  external  coverings,  as  in  the  mollusca.     These  salts 
have  been  already  described  under  their  proper  heads,  in 
the  Inorganic  Chemistry,  and  their  relations  to  life  will  be 
considered  in  the  section  on  the  nutrition  of  animals  and 
Dlants. 

Laws  of  Chemical  Transformations. 

642.  The  various  changes  met  with  in  the  study  of  or- 
ganic  substances,  resulting  in  the  destruction  of  existing 
combinations,  and  the  formation  of  new  ones,  may  conve- 
niently be  reduced  to  two  classes;  first,  equivalent  substitu- 
tions) and  second,  direct  union.     It  will  be  shown  that,  in 
the  first  case,  decomposition  and  recomposition  are  reciprocal 
and  simultaneous,  so  that  the  one  implies  the  other,  and  we 
investigate  at  once  the  laws  of  both.     In  the  second  case, 
this  relation  apparently  does  not  exist;  but  there  is  a  direct 


830  ORGANIC   CHEMISTRY. 

decomposition,  which  is  the  converse  of  direct  union,  and 
consists  in  the  partition  or  dissection  of  a  compound  into 
two  or  more  compounds  having  a  lower  equivalent. 

JEJq uit'a len t  Su. Ijstitu tio n . 

643.  The  law  of  substitution  is,  that  one  or  more  atoms 
of  an  element  in  a  compound  may  be  replaced  by  any  other 
element,  or  group  of  elements,  which  are  equivalent  in  their 
chemical  relations ;  and  the   chemical  constitution  of  the 
compound  remain  unchanged.     Thus  acetic  acid  C4H4O4 
may  lose  three  atoms  of  hydrogen  and  take  in  their  place 
three  equivalents  of  chlorine,  which  last  are  substituted  for 
the  hydrogen,  without  changing  the  acid  constitution  of  the 
body  j    the  new   compound,  cliloracetic  acid,   C4(HC13)04 
closely  resembles  acetic  acid  in  its  properties.     Here  85-5 
parts  of  chlorine  are  equivalent  to  1  of  hydrogen,  and  C13  is 
equivalent  to  H3,  and  may  be  substituted  for    it  without 
altering  the  1ypc  of  the  compound.     Bromine  and  iodine, 
and  perhaps  fluorine,  may  replace  hydrogen  in  a  similar 
manner. 

644.  In  the  foregoing  reaction  C4H404  and  Clfi  are  con- 
cerned, and  C4(HCl3)04  and  3(ClH)  are  the  results.     We 
shall  show  farther  on,  from  a  consideration  of  their  combining 
volumes,  that  as  the  equivalent  volume  of  chlorohydric  acid 
is  (HC1),  that  of  hydrogen  is  (HH),  and  that  of  chlorine 
(C1C1).     In  the  reaction  between  acetic  acid  and  chlorine, 
there  are  then  but  three  equivalents  or  volumes  of  chlo- 
rine, 3(C1C1),  and  each  successive  volume  exchanges  one* 
of  its  atoms  for  one  of  hydrogen:  thus,  (C4H404)-f(ClCl) 
=(C4H3Cl04)-f  (C1H)— and  so  on  with  a  second  and  third 
volume  of  chlorine.     In  many  instances  we  can   trace  the 
successive  steps  by  which  atom  after  atom  of  hydrogen  is 
replaced  by  chlorine,  a  corresponding  equivalent  of  hydro- 
chloric acid  being  simultaneously  formed.     The  law  of  equi- 
valent substitution  is  then   reducible    to    that  which    has 
been  called  double  elective  affinity,  and  always  supposes  the 
reaction  of  two  complex  bodies,  which  give  rise  to  two  new 
ones. 

645.  As  hydrogen  is  replaceable  by  Cl,  Br,  and  I,  so 
oxygen  is  capable  of  being  replaced  by  sulphur,  selenium, 
and  tellurium.     This  can  seldom  be  effected  directly,  as  in 
the  case  of  chlorine  and  hydrogen,  but  it  is  obtained  by  in- 
direct decompositions.    Alcohol,  which  is  C4H602,  gives  sul- 


EQUIVALENT    SUBSTITUTION.  381 

pkur  alcohol,  C4H8Sa,  and  the  selenium  compound  will  bo 
C4H6Se2.  Mineral  chemistry  affords  similar  instances; 
sulphate  of  soda  is  2S03-f-2NaO,  or  S2Na308,  while  the  hypo- 
sulphite of  soda  is  S2Na3(02S6),  and  another  salt  is  S0Naf 
(O4S4).  These  different  sulphates  crystallize  with  the  same 
amount  of  water,  have  the  same  form,  and  the  same  solu- 
bility. 

Nitrogen,  phosphorus,  arsenic,  and  antimony,  which  form 
a  natural  group,  may  also  replace  each  other,  equivalent  for 
equivalent;  thus,  ylycocoll,  which  is  C4H5N04,  has  a  corre- 
sponding arsenical  compound,  alkargene,  C4H5As04. 

646.  When  any  acid,  like  chlorohydric  or  acetic  acid,  acts 
upon  a  metal  such  as  zinc,  hydrogen  is  evolved,  and  a  chlo- 
rid  or  acetate  of  zinc  is  formed,  in  which  Zn  has  replaced 
the    hydrogen,  HCl-f  Zn=H-f  ZnCl,  and  C4H404-|-Zn== 
C4H3ZnO4-f-H.     If  chlorine  (C1C1)  acts  upon  zinc,  we  ob- 
tain the  same  chlorid  as  with  chlorohydric  acid,  (ClCl)-j-Zn2 
— 2(ZnCl),  and  when  chlorine  combines  with  hydrogen,  it  is 
(ClCl)-f  (HH)=2(HCi).  Now  as  the  action  of  HC1  upon  zinc 
evolves  hydrogen  (HH),  all  these  analogies  lead  us  to  conclude 
that  the  equivalent  of  zinc  is  Zn2=(ZnZn),  and  hence  that 
in  the  case  of  acetic  or  chlorohydric  acids,  an  equivalent  of 
zinc  reacts  with  two  equivalents  of  the  acid.     Acetic  acid 
C4H4O4-f  ZnZn=C4(H3Zn)04+  (ZnH),  but  ZnH  with  an- 
other equivalent  of  C4H404  yields  a  second  equivalent  of 
acetate  and  one  of  hydrogen  (HH).     The  hydrates  of  metals 
like  ZnH  are  seldom  stable,  and  as  they  decompose  water 
.and  acids  very  readily,  are  difficult  to  be  isolated.     The  re- 
placement of  the  hydrogen  in  acids  by  a  metal  is  then  ana- 
logous to  that  of  its  substitution  by  chlorine. 

647.  When  an  acid  is  brought  in  contact  with  a  metallic 
oxyd,  double  decomposition  ensues    in  the  same  manner, 
but  with  the  formation  of  an  oxyd  of  hydrogen;  acetic  acid 
C4H404-fZnO:=C4H3Zn04-f HO.     But  with  the   equiva- 
lents here  proposed,  the  composition  of  oxyd  of  zinc  must 
be  written  Zna02,  and  that  of  water  H202,  so  that  as  in 
the  reaction    with   metallic  zinc,  two  equivalents  of   the 
acetic  acid  react  with  Zn303.     If  we  represent  the  actions 
as  consecutive,  the  first   result  will  be  (ZnH)02,  or   the 
hydrated  oxyd  of  zinc,  corresponding  to  ZnH,  which  with 
another  equivalent  of  acid  exchanges  its  Zn  for  H,  forming 
water,  (H90a). 

648.  All  the  metals  proper  are  capable  of  replacing  in  this 


382  ORGANIC   CHEMISTRY. 

manner  a  portion  of  the  hydrogen  of  acids  to  form  salts. 
A  great  number,  like  acetic  acid,  have  only  one  atom  of 
hydrogen  which  can  be  replaced  by  a  metal,  but  in  others 
two  and  three  atoms  may  be  in  a  similar  manner  replaced. 
These  are  called  bibasic  and  tribasic  acids ;  while  such  as 
acetic  acid  are  said  to  be  monobasic.  Tartaric  acid  is  bibasic; 
its  composition  is  represented  C8H6012,  or  C8H4(H2)012; 
the  two  equivalents  of  hydrogen  may  be  replaced  by  two 
equivalents  of  some  metal  as  CsH4Zn2012;  by  two  dif- 
ferent metals  as  in  CsH4(KNa)Oia,  or  but  one  equivalent 
may  be  replaced  as  in  C8H4(HK)012.  The  latter  still 
retains  acid  properties,  and  is  called  an  acid  salt.  The  salts 
of  tribasic  acids  may  contain  either  one,  two,  or  three  equiva- 
lents of  hydrogen  replaced  by  a  metal;  the  first  two  of 
these  salts  will  be  acid,  and  the  last  neutral. 

The  monobasic  acids  are  almost  always  volatile,  while 
the  bibasic  and  tribasic  acids  are  never  volatile  without 
decomposition. 

649.  The  sesquioxyds,  which  have  been  represented  in 
treating  of  mineral  chemistry  as  composed  of  two  equivalents 
of  a  metal  combined  with  three  of  oxygen,  offer  a  peculiar 
case  in  the  formation  of  salts.  If  we  take,  for  example,  the 
peroxyd  of  iron,  Fea03,  we  find  that  it  saturates,  not  twc 
equivalents  of  acetic  acid,  but  three,  and  that  while  in  the 
acetate  of  the  protoxyd  of  iron  FeO  replaces  H,  in  the  acetate 
of  the  peroxyd  two-thirds  of  an  equivalent  of  iron  sustain  the 
same  relation ;  if  then  we  would  represent  the  acetate  of  the 
peroxyd,  we  must  write  it  C4H3Fef04.  In  other  words 
Fe203  has  reacted  as  if  it  were  3(Fef  0).  But  if  we  ex- 
amine these  two  salts  still  farther,  we  find  that  in  their  che- 
mical reactions  they  differ  from  each  other  as  widely  as  tho 
salts  of  two  distinct  metals,  and  that  we  have  in  the  salts  of 
the  peroxyd,  iron  with  two-thirds  its  ordinary  equivalent,  and 
with  peculiar  and  distinct  properties.  We  may  designate 
the  iron  in  the  proto-salts  as  ferrosum,  with  an  atomic  weigh! 
of  28  and  the  symbol  Fe,  and  the  iron  in  the  persalts  as 
ferricum,  with  an  atomic  weight  of  18*6,  and  write  its 
symbol,  fe.  The  sesquioxyd  of  iron,  Fe203,  is  then  3(feO) 
and  the  corresponding  acetate  of  ferricum  C4H3fe04. 

This  same  view  is  to  be  extended  to  the  proto  and  ses 
qui-salts  of  chromium  and  manganese,  and  to  the  salts  of 
alumina,  which  is  a  sesquioxyd;  also  to  the  salts  of  mercury 
and  of  tin,  in  which  the  equivalents  of  the  two  forms  are  to 


EQUIVALENT    SUBSTITUTION.  383 

each  other  as  1  :  2.  We  have  ckromosum  and  cJiromicum} 
aluminicum,  stannosum  and  stannicum,  mercurosum  and 
mercuricum;  the  second  form  of  the  metal  is  distinguished 
by  writing  its  symbol  with  a  small  letter  as  Cr,  cr,  al,  Su, 
sn,  Hg,  hg,  &c. 

650.  We  have  seen  that  acetic  acid  may  exchange  three 
equivalents  of  hydrogen  for  chlorine,  and  but  one  equiva- 
lent for  a  metal,  so  that  in  chloracetate  of  silver,  C4C13  Ag04, 
all  the  hydrogen  is  replaced.     There  are  many  acids  in 
which  we  cannot  effect  the  substitution,  by  chlorine,  nor  can 
the  fourth  atom  of  hydrogen  in  acetic  acid  be  thus  replaced; 
it  can  be  removed  only  by  substituting  a  inetal.     Thus  the 
hydrogen  which  is  replaceable  by  chlorine  is  distinct  from 
that  which  is  equivalent  to  a  metal.     It  will  be  shown  far- 
ther on,  however,  that  there  are  some  bodies  in  which  this 
distinction  appears  to  be  lost,  and  in  which  all  the  hydrogen 
may  be  replaced  either  by  chlorine  or  a  metal. 

651.  In  treating  of  the  action  of  chlorine  upon   acetic 
acid,  we  have  considered  the  process  only  with  reference  to 
the  acid ;   but  the   substitution  is  reciprocal,  and  there  is 
mutual  decomposition.     To  make  the  question  more  simple, 
we  will  select  a  case  where  but  one  atom  of  hydrogen  is 
replaced.     The  essence  of  bitter  almonds,  benzoilol,  has  the 
composition  C14H8Oa;  by  the  action  of  chlorine,  hydrochlo- 
ric acid  is  formed,  and  one  atom  of  hydrogen  is  replaced  by 
chlorine,  C14H803+(ClCl)=C14H5Clp3-hHCl.    Now  if  we 
consider   only  the  oil,  it  will   be  said   that  an  equivalent 
substitution  has  taken  place  of  Cl  for  H ;   but  it  is  equally 
correct  to  say,  that  the  benzoilol  minus  H  has  replaced  Cl  in. 
the  equivalent  of  chlorine  (C1C1)  ;  in  other  words,  that  the 
essence  has  ceded  H  to  form  hydrochloric  with  Cl,  and  that 
the  residue  has  replaced  the  eliminated  atom  of  chlorine. 

When  the  constitution  of  the  bodies  becomes  more  com- 
plex, the  action  is  still  the  same;  benzoilol  reacts  with  nitric 
acid,  which  is  NHO<j,  and  yields  water  and  a  new  substance 
containing  the  elements  of  the  essence  and  the  acid,  minus  an 
equivalent  of  water;  C14H602-}-NHOG=:C14H5N06H-Ha03. 
An  examination  of  this  reaction  leads  to  the  conclusion 
that  the  acid  has  furnished  H  and  the  essence  H03  to 
form  the  equivalent  of  water ;  so  that  the  residues  C14Hb 
and  N06  unite  to  form  the  new  product;  and  it  may  be 
said  that  C14H5  replaces  H  in  the  nitric  acid,  precisely  aa 
C14H3Oa  replaces  Ci  in  the  equivalent  of  chlorine. 


ORGANIC   CHEMISTRY. 

652.  The  monobasic  nitric  acid  has  fixed   tho  elements 
of  a  neutral  body   in   place  of  its  atom  of  hydrogen,  and 
the  nitrobenzoilol  is  hence   neutral.     But  if  benzoic  acid, 
which  is  monobasic,  be  substituted  for  the  essence,  it  pre- 
serves even  in  combination  its  saline  character;  and  hence  the 
compound  has  the  monobasic  character  which  pertains  to  the 
benzoic  acid.     And  even  if  this  nitrobenzoic  compound  re- 
places the  hydrogen  of  a  second  atom  of  nitric  acid,  the  mono- 
basic character  is  still  preserved  in  the  resulting  compound. 
A  bibasic  acid,  like  the  sulphuric,  will  form  with  one  equiva- 
lent of  a  neutral  substance  a  monoba*sic  acid;  and  with  two, 
a  body  which  shall  itself  be  neutral ;  because  in  these  cases, 
one  and  two  atoms  of  hydrogen  have  been  removed  from  the 
acid.     But  if  an  equivalent  of  a  monobasic  acid  reacts  with 
sulphuric  acid,  it  still  retains  its  saline  power  in  combina- 
tion, and  the  result  is  bibasic  :  in  like  manner,  with  another 
bibasic  acid,  sulphuric  acid  yields  a  compound  which  is  triba- 
sic.    In  all  these  reactions,  as  in  the  formation  of  nitroben- 
zoilol, corresponding  equivalents  of  H203are  eliminated,  and 
the  derived  bodies  are  often  designated  as  coupled  acids. 

653.  Some  writers  have  distinguished  these  cases  from  the 
simpler  instances  of  equivalent  substitution,  and  have  desig- 
nated them  as  substitutions  ~by  residues.     But  this  distinction 
originates  in  a  too  much  restricted  idea  of  the  meaning  of 
an   equivalent.     In    an  early    period    of  the    science,    the 
equivalent  of  a  metal  was  fixed  from  the  proportion  of  hydro- 
gen it  replaces,  or  in  other  words  from  the  composition  of 
its  salts;  but  we  have  since  learned  that  although  28  parts 
of  manganese  are  generally  equivalent  to  1  of  hydrogen  and 
35-5  of  chlorine,  there  are  cases  where,  as  in  permanganic 
acid,  which    corresponds   to    perchloric  acid,   56  parts  of 
manganese  are  equivalent  to  35-5  of  chlorine;  and  in  the 
sesqui-salts  of  the  metal,  18 -6  of  manganese  become  equiva- 
lent to  H;  so  31-7  parts  of  copper  are  at  one  time  equiva- 
lent to  one  of  hydrogen,  and  634  parts  at  another  time. 
Hence  the  numbers    assigned   as   the  equivalents  of  the 
elements  are  changeable   as  these   elements  change   their 
functions,  and,  as  in  the  case  of  benzoilol,  groups  of  carbon 
and  hydrogen,  or  carbon,  hydrogen,  and  oxygen,  may  become 
equivalent  to   a  single   atom  of  chlorine  of  hydrogen  or  a 
metal,  and  may  replace  it  in  combination. 

These  groups  which  replace  the  metals  on  the  one  hand, 
and  chlorine  and  bromine  on  the  other,  have  been  described 


EQUIVALENT   SUBSTITUTION.  385 

by  some  authors  by  the  name  of  compound  radicals,  and 
have  served  as  the  basis  of  a  system  of  organic  chemistry 
and  of  nomenclature.  But  as  we  conceive  that  the  system 
is  liable  to  great  objections,  and  tends  to  perpetuate  false 
notions  of  the  science,  the  language  of  the  compound  radi- 
cal theory  will  not  be  employed  in  these  pages. 

654.  Tlie  law  of  direct  union  is  much  more  simple.     A 
salt  may  assimilate  the  elements  of  water,  or  of  a  metallic 
oxyd,  or  ammonia  may  combine  with  an  acid,  as  with  hydro- 
chloric acid,  to  form  sal-ammoniac;  NH3-j-HCl  — NH4C1. 
A   carbon   compound,   like   olefiant   gas,  C4H4,  may  also 
unite  directly  with  C13,  to   form  C4H4C13.     In  these  and 
similar  instances  there  is  only  one  product,  a  character  by 
which   such  reactions  are  distinguished  from  those  of  the 
first  class.     On  the  other  hand,  a  body  may  eliminate  the 
elements  of  water  or  of  hydrogen,   or  some  similar  sub- 
stance, and  thus  resolve  itself  into  two ;  for  instance,  alcohol 
C4H602,  under  the  influence  of  certain  reagents,  may  lose 
H2,  and  in  some  of  its  combinations  is  resolved  by  heat 
into  C4H4,  and  H303.     Many  ammoniacal  salts  which  are 
formed  by  direct  union  of  the  acid  and  ammonia,  separate 
under  the  influence  of  heat  into  water,  and  new  compounds 
called  amids,  which,  when  placed  in  contact  with  water, 
under  proper  conditions,  combine  with  that  substance,  and 
regenerate  the  original  salts. 

655.  The  compounds  formed  by  direct  union  may  then 
divide  in  a  manner  different  from  that  of  their  composition, 
and  thus  produce  two  new  compounds  unlike  the  parent 
ones,  precisely  as  in  the  reactions  of  the  first  class.     We 
hence  arrive  at  the  conclusion,  that  the  phenomena  of  the 
second  class  represent  only  an  intermediate  step  in  the  pro- 
cess of  equivalent  substitution ;  and  that  if  we  could  arrest 
the  latter  process,  we  should  always  find  it  to  consist  of  two 
parts,  composition  and  decomposition,  resulting  in  a  mutual 
substitution.     As  an  illustration,  may  be  cited  the  com- 
pound formed  by  the  direct  combination  of  chlorine  with 
olefiant  gas,  which  is  C4H4C12,  but  under  certain  circum- 
stances is  decomposed  into  HC1  and  C4H3C1 ;  the  latter  is  a 
substitution  product  from  olefiant  gas,  and  we  are  here  enabled 
to  see  the  intermediate  step  in  its  formation. 

The  two  classes  into  which  we  have  for  convenience  di- 
vided the  phenomena  of  chemical  transformations,  are  then 
reducible  to  one  simple  formula;  a-}-b  and  c-\-d  may  unite 

25 


,386  ORGANIC    CHEMISTRY. 

to  form  a-\-b-]-c-\-d,  and  may  afterward  be  rearranged  so  as 
to  form  a-J-c  and  b-\-d,  as  in  the  first,  or  a-\-b  and  c-\-dy  as  in 
the  second  case. 

On   Combinations    by    Volumes. 

656.  The  law  of  combination  by  volumes  has  already 
been  given  in  the  first  portion  of  this  work  (257);  but  we 
refer  to  it  again  to  explain  the  density  of  vapours,  and  the 
equivalents  of  organic  substances. 

The  proportions  in  which  oxygen  and  hydrogen  unite  to 
form  water  are  one  volume  of  the  former  to  two  volumes 
of  the  latter,  and  these  three  are  condensed  into  two  volumes 
of  the  vapor  of  water  at  21*2°  F.  As  these  proportions  have 
been  assumed  to  correspond  to  one  equivalent  of  each,  the 
composition  of  water  is  written  HO,  having  an  equivalent 
number  of  l-f-8  =  9,  and  corresponding  to  two  volumes  of 
vapor. 

The  specific  gravity  of  hydrogen  has  been  found  by  experi- 
ment to  be  69-2,  air  being  1000,  while  oxygen  is  1105-6. 
Then 

2  volumes  of  hydrogen  2X69-2 138-4 

1         "       of  oxygen 1105-6 

yield  2  volumes  of  vapor  water 1244*0 

1         «       of    do.       do 622-0 

Experiment  gives  for  the  density  of  water  vapor  620-1. 

657-  Density  of  Carbon  Vapor. — In  calculating  the  atomic 
volume  of  bodies  of  the  carbon  series,  it  becomes  necessary 
to  fix  upon  the  density  of  carbon  vapor;  but  as  carbon  is 
not  known  in  a  gaseous  form,  we  must  deduce  its  density 
from  that  of  some  one  of  its  compounds. 

When  carbon  is  burned  in  oxygen  gas,  this  is  converted 
into  carbonic  acid  gas  without  change  of  volume.  If  we 
subtract  from  the  weight  of  the  new  compound  that  of  the 
oxygen,  we  shall  then  have  the  weight  corresponding  to  the 
carbon  vapor.  Experiment  has  given  for  the  density  of 

Carbonic  acid  gas  (air=1000) 1529-0 

Deduct  that  of  oxygen 1105-6 

Gives  for  the  density  of  carbon  vapor 423-4 

If  we  suppose  the  gas  to  consist  of  two  volumes  of  carbon 
vapor  and  two  of  oxygen  condensed  one-half,  the  equivalent 
volume  of  carbon  will  be  the  same  as  that  of  hydrogen,  and 
its  weight  represented  by  the  above  number.  But  if  it 
may,  with  as  good  reason,  be  regarded  as  formed  by  the  con 


DIVISIBILITY   OP   FORMULAS.  887 

densation  of  two  volumes  of  oxygen  and  one  of  carbon  vapor 
into  two  volumes,  the  density  of  carbon  vapor  will  be  twice 
the  number  calculated,  or  846 -8. 

The  experimental  density  of  carbonic  acid  is,  however, 
not  very  exact,  and  the  density  of  carbon  vapor  may  bo 
more  accurately  calculated  from  the  well-determined  density 
of  oxygen.  Carbonic  acid  consists  of  oxygen  72-73  and 
carbon  27-27  parts,  and  the  observed  density  of  oxygen  is 
1105-6;  we  have  then  this  proportion: 

72-73:  27-27::  1105-6:  x. 

in  which  x  =  829,  which  we  shall  adopt  as  the  most  correct 
number  for  the  density  of  carbon  vapor. 

658.  Hence,  if  we  know  the  composition  and  equivalent 
of  any  body,  we  can  calculate  its  density;  or,  having  the 
density  and  composition  given,  can  fix  its  equivalent.  '  For 
example,  the  density  of  olefiant  gas,  as  found  by  experiment, 
is  9674.    It  consists  of  equal  equivalents  of  carbon  and  hy- 
drogen, and  one  volume  of  it  contains 

2  volumes  of  hydrogen  =  1  eq.  2X69-2 138'4 

1         "       of  carbon  vapor  =  1  eq 829-0 

Yield  1  volume  of  olefiant  gas 967'4 

If  now  the  equivalent  of  olefiant  gas  be  like  that  of  water 
represented  by  two  volumes,  the  formula  will  be  C2H2;  but 
most  writers  have  assumed  four  volumes  as  representing  the 
equivalent  of  organic  compounds;  while  water  is  written  HO, 
and  corresponds  to  but  two  volumes  of  vapor.  Thus  the 
the  formula  of  olefiant  gas  is  generally  written  C4H4  =  four 
volumes  of  vapor ;  to  be  compared  with  this,  water  must  be 
H20a.  Some  of  the  French  chemists,  choosing  to  preserve 
the  old  equivalents  of  organic  bodies,  have  doubled  in  this 
manner  that  of  water;  while  others  have  preferred  to  divide 
the  formulas  of  organic  substances,  and  reduce  all  to  the 
standard  of  two  volumes,  oxygen  being  one;  or,  in  other 
words,  to  take  the  vplume  of  the  atom  of  hydrogen  as  unity. 
We  shall  in  these  pages  regard  H2,  which  is  equivalent  to 
four  volumes,  (0  being  one  volume,)  as  unity,  and  write  the 
formula  of  water  HaOa,  with  an  equivalent  of  18. 

On  the  Law  of  the  Divisibility  of  Formulas. 

659.  The  researches  of  Gerhard  t  and  Laurent  have  esta- 
blished a  very  important  law  which  prevails  in  the  grouping  of 
elements  in  compounds,  not  only  in  those  of  the  carbon  series, 


388  ORGANIC   CHEMISTRY. 

but  also  in  mineral  chemistry.  It  is,  that  in  all  compounds 
of  carbon,  hydrogen,  and  oxygen,  represented  by  an  equiva- 
lent of  four  volumes  of  vapor,  the  number  of  atoms  of  carbon 
and  oxygen  is  always  divisible  by  two,  and  that  of  the  atoma 
of  hydrogen  by  the  same  number.  If  the  oxygen  is  wholly 
or  in  part  replaced  by  sulphur  or  selenium,  the  substitution 
is  always  atom  for  atom,  so  that  the  same  divisibility  is 
maintained;  and  if  the  hydrogen  is  replaced  in  whole  or  in 
part  by  chlorine,  iodine,  or  bromine,  by  nitrogen,  phospho- 
rus, arsenic,  or  antimony,  or  by  any  of  the  metals,  the  sum 
of  the  number  of  the  atoms  will  always  be  a  multiple  of  two. 

On  Isomcrism. 

660.  We  haye  seen,  in  treating  of  substitution,  that  a  num- 
ber of  the  atoms  of  any  element  in  a  compound  may  be  re- 
placed by  another  element,  and  the  constitution  of  the  body 
remain  unchanged.  From  this,  and  from  other  facts,  we  con- 
clude that  the  properties  of  compounds  depend  rather  irpon  the 
peculiar  arrangement,  than  upon  the  species  of  their  consti- 
tuent atoms;  and,  moreover,  that  a  different  arrangement  of 
the  same  elements  may  form  compounds  very  different  in 
their  properties.  Such  bodies  are  frequently  met  with  among 
the  carbon  series,  and  are  denominates  isomeric  compounds, 
(from  isos,  equal,  and  mcros,  measure.)  We  have  an  instance 
in  the  essence  of  spiraea  ulmaria,  and  benzoic  acid,  both  of 
which  are  represented  by  the  formula  C14H604,  but  are  very 
distinct  in  their  characters.  The  relation  of  such  as  have 
not  only  the  same  proportional,  but  the  same  actual  com- 
position, may  be  distinguished  by  the  term  metamerism, 
(from  meta,  by,  and  meros,  measure.) 

Another  form  of  isomerism  is  that  in  which  the  relative 
proportions  of  the  elements  being  the  same,  the  equivalent 
of  the  one  is  a  multiple  of  the  other.  Thus,  olefiant  gas 
C4H4,  butyrene  CSH8,  naphtene  016H10,  and  cetene  C33H33, 
have  the  same  proportions  of  carbon  and  hydrogen,  though 
each  has  a  density  and  equivalent  double  that  of  the  pre- 
ceding; such  bodies  are  said  to  be  polymeric,  (frompolus, 
many,  and  meros.) 

The  phenomena  which  in  mineral  chemistry  have  been 
characterized  under  the  names  of  dimorphism  and  allotro- 
pism  are  instances  of  isomerism  which  is  often  polymeric,  and 
are  met  with  even  among  bodies  which  are  considered  as 
elementary. 


CHEMICAL   HOMOLOGUES.  389 

On  Chemical  Homologues. 

661.  The  carbo-hydrogens  just  mentioned,  whose  com- 
position is  represented  by  a  multiple  of  C4H4,  are  possessed 
of  similar  chemical  affinities,  and  form  with  other  substances 
similar  compounds.    Two  of  them,  the  first  and  last,  are  arti- 
ficially formed  from  compounds  which  have  the  formulae 
C4H603  and  C33H3403,  and  differ  from  their  respective  hydro- 
carbons only  by  the  elements  of  water. 

These  compounds  are  two  terms  of  a  series  of  bodies  which 
are  known  as  alcohols,  from  common  alcohol,  which  was  the 
first  known  of  the  series.  The  first  one  has  the  formula 
C3H403  =  C3H3-f  H302,  and  the  next  C4H603,  each  one  dif- 
fering from  the  last  by  C3H3;  so  that  representing  by  n  any 
number  divisible  by  two,  the  general  formula  of  the  series 
will  be  CnHn-|-HflOa,  or  CnHfl+303.  Bodies  thus  related 
are  designated  homoloyues;  and  the  study  of  this  relation- 
ship, which  was  first  pointed  out  by  Gerhardt,  is  of  the  high- 
est importance  to  the  science. 

The  bodies  of  an  homologous  series  generally  undergo  simi- 
lar changes  by  like  reagents,  and  the  products  resulting  are 
also  homologous.  Thus,  wine  alcohol,  by  oxydizing  agencies, 
loses  H2,  and  forms  the  body  C4H403;  by  further  oxydation 
it  yields  acetic  acid  C4H404;  and  every  alcohol  in  like  man- 
ner yields  an  acid  homologous  with  the  acetic  acid :  the  ge- 
neral formula  of  the  series  being  CnHn04.  The  intermediate 
body  CMHM03  has  not,  however,  in  all  cases  been  obtained. 

The  alcohols  also  yield  a  series  of  homologous  alkaloids, 
whose  common  formula  is  (CnHM)H3N  or  CnHn+3N. 

662.  In  many  homologous  series  the  number  of  equiva- 
lents of  hydrogen  is  not  equal  to  that  of  the  carbon,  and 
the  formula  must  be  written  differently.    Thus,  benzoic  acid 
C14H604  and  cuminic  acid  C20H1304  are  homologous,  and 
differ  from  each  other  by  (C3H3)3,  and  we  may  express 
them  by  the  general  formula  CnHn_804,  the  number  of  equi- 
valents of  hydrogen  being  less  by  eight  than  that  of  carbon : 
by  this  it  will  be  seen  that  the  lowest  term  of  the  series  will 
be  that  in  which  n  —  8=2,  or  C10H304;  for  if  n  —  8—  zero, 
the  compound  will  contain  no  hydrogen,  and  hence  want  the 
^characteristic  properties  of  an  acid  which  belong  to  the  series. 
If,  however,  the  hydrogen  be  present  in  excess,  the  case  will 
be  different.     In  the  formula  of  the  alcohols,  if  n  =  zero,  the 
representative  of  the  type,  is  Ha03,  or  water,  which  is  the 


390  ORGANIC   CHEMISTRY. 

prototype  of  the  alcohol  series;  and  in  the  alkaloids  of  tho 
same  group,  when  n  =  zcro,  we  have  NH3,  or  ammonia,  which 
is  equally  their  prototype. 

It  will  be  seen  from  what  we  have  said  of  isomeric  bodies 
that  there  may  be  two  or  more  series  of  homologous  bodies, 
which  shall  be  metameric  of  one  another,  and  hence  simi- 
larity of  chemical  characteristics  is  necessary  to  constitute  a 
homology.  In  an  homologous  series  of  chemically  allied 
compounds,  then,  while  the  oxygen  and  nitrogen  always 
remain  the  same,  the  proportions  of  hydrogen  and  carbon 
vary  by  a  simple  and  constant  ratio. 

Temperature  of  Ebullition. 

663.  A  simple  relation  between  the  boiling  points  of 
different  members  of  an  homologous  series  has  been  pointed 
out,  which  may  often  serve  an  important  end  in  deciding  the 
equivalent  of  a  compound.     The  boiling  point  of  the  volatile 
acids  of  the  formula  CnHn04  is  found  to  increase  about 
36°  F.  for  each  addition  of  C2Ha. 

ANALYSIS  OF  ORGANIC  SUBSTANCES. 

664.  The  ultimate  analysis  of  organic  substances  is  of 
great  importance  :  for  as  we  are  unable  to  form  them  by  a 
direct  combination  of  their  elements,  a  correct  understanding 
of  their  composition,  and  of  the  nature  of  the  changes  which 
they  undergo,  must  depend  entirely  on  the  results  of  their 
analysis.     The  equivalent  of  many  substances  is  so  large, 
that  a  change  of  one-hundredth  part  in  the  proportions,  gives 
to  the  compound  entirely  distinct  properties.     Great  refine- 
ment is  consequently  necessary  in  analysis,  to  enable  us  to 
detect  the  minute  differences  in  composition ;  and  such  have 
been  the  care  and  skill  with  which  the  subject  has  been 
studied,  that  we  have  now  arrived  at   very    great   accuracy 
in  operations  of  this  kind. 

665.  In  theory,  the    process  of  organic  analysis  is  ex- 
ceedingly simple.     If  any  organic  substance,  as  sugar,  for 
example,  is  heated  with  a  body  capable  of  yielding  oxygen, 
such  as  the  oxyd  of  copper,  of  lead,  or  any  other  easily  re- 
ducible metal,  it  is  completely  decomposed  ;  the  carbon  and 
hydrogen  take  oxygen  from  the  metallic  oxyd,  and  are  wholly 
converted  into  carbonic  acid  and  water.     From  the  weight 
of  these,  it  is  easy  to  calculate  the  amount  of  carbon  and 
hydrogen  in  the  body,  and  if  it  contains  no  other  element 


ANALYSIS   OF   ORGANIC   SUBSTANCES.  391 

except  oxygen,  this  is  known  by  the  loss.  But  notwith- 
standing the  theoretical  simplicity  of  the  process,  its  accurate 
execution  is  exceedingly  difficult,  and  very  many  precautions 
are  necessary  to  insure  accuracy.  It  is  not  the  object  of  this 
work  to  explain  all  the  precautions  necessary  to  the  successful 
performance  of  analytical  operations,  but  merely  to  give  an 
outline  of  the  method  pursued,  and  a  general  idea  of  the  means 
employed.  For  more  particular  information,  the  student  is 
referred  to  an  excellent  memoir  on  this  subject,  by  Liebig. 
666.  The  operation  is  performed  in  a  combustion  tube  of 
hard  glass,  from  12  to  18  inches  in  length,  and  from  T40  to  -fa 
of  an  inch  in  diameter.  One  end  is  drawn  out  to  a  point, 
turned  aside  and  sealed.  Oxyd  of  copper,  prepared  from 
the  nitrate,  is  generally  employed  for  the  combustion. 
Just  before  using  it,  it  is  heated  to  redness,  in  order  to  expel 
the  moisture  which  it  readily  attracts  from  the  atmosphere ; 
the  combustion  tube  is  then  about  two-thirds  filled  with  the 
hot  oxyd.  The  substance  to  be  analyzed  having  been  care- 


Oxyd.  Mixture.  Oxyd. 

Fig.  394. 

fully  dried,  five  or  six  grains  of  it  are  weighed  out  in  a  tube 
with  a  narrow  mouth,  in  order  to  prevent  the  absorption  of 
moisture.  It  is  then  rapidly  mixed  in  a  warm  and  dry  por- 
celain mortar,  with  the  greater  portion  of  the  oxyd  from  the 
tube,  to  which  it  is  again  transferred,  and  the  tube  is  then 
nearly  filled  up  with  pure  oxyd.  The  relative  portions  of 
the  oxyd  and  mixture  are  shown  in  fig.  394. 

667.  However  carefully  the  mixture  has  been  made,  a 
little  moisture  will  have  been  absorbed  from  the  air,  which 
must  be  removed 'by  the  following  arrangement: — To  the 
end  of  the  combustion  tube  is  fitted,  by  means  of  a  cork,  a 
long  tube  filled  with  chlorid  of  calcium,  and  to  this  is  at- 
tached a  small  air-pump,  fig.  395.  The  combustion  tube  is 
covered  with  hot  sand,  and  the  air  slowly  exhausted.  After 
a  short  time,  the  stopcock  is  opened,  and  the  air  allowed  to 
enter,  thoroughly  dried  by  its  passage  over  the  chlorid  of 
calcium.  It  is  again  exhausted,  and  this  process  repeated 
four  or  five  times,  by  which  the  mixture  is  completely  dried. 


392 


ORGANIC   CHEMISTRY. 


Fig.  395. 

668.  The  tube  is  now  ready  for  the  combustion,  and  is 

placed  in  tho 
furnace,  figure 

396-  This  is 

constructed  of 
sneet  iron,  and 
Fig.  396.  fitted   with    a 

series  of  supporters  at  short  distances  from  each  other,  to 
prevent  the  tube  from  bending  when  softened  by  heat.  The 
furnace  is  placed  on  a  flat  stone,  or  tile,  with  the  front 
slightly  inclined  downward.  The  quantity  of  water  form- 
ed in  the  process  is  estimated  by  a  light  tube,  fig.  397, 

which   is  filled   with  frao;- 

ments  of  chlorid  of  calciuil)j 

Fig.  397.  and,  after  having  been  very 

carefully  weighed,  is  attach- 
ed by  a  well-dried  and  closely  fitting  cork,  to  the  end  of 
the  combustion  tube.  To  determine  the  carbonic  acid,  a 
small  five-bulbed  tube  of  peculiar  form  is  used,  called  Liebig's 
potash  bulb  tube,  fig.  398.  It  is  charged  for 
this  purpose  with  a  solution  of  caustic  potash  of 
a  specific  gravity  about  1-25,  with  which  the 
three  lower  bulbs  are  nearly  filled.  Its  weight 
is  determined  with  great  exactness,  and  it  is 
then  attached  to  the  chlorid  of  calcium  tube, 
by  a  little  tube  of  gum  elastic,  which  is  held 
fast  by  a  silken  cord.  The  whole  arrange- 
ment is  shown  in  fig.  399.  The  tightness  of 
Fig.  398.  the  junction  is  ascertained  by  drawing  a  few 


ANALYSIS   OF   ORGANIC    SUBSTANCES.  398 


Fig.  399. 

bubbles  of  air  through  the  end  of  the  potash  tube,  so  that  the 
liquid  will  be  raised  a  few  inches  above  the  level  on  the 
other  side ;  if  this  level  remains  the  same  for  some  minutes, 
the  whole  apparatus  is  tight.. 

669.  Heat  is  now  applied  by  means  of  ignited  charcoal 
placed  around  the  anterior  portion  of  the  tube,  and  when 
this  is  red-hot,  the  fire  is  gradually  extended  along  the  tube, 
by  means  of  a  movable  screen,  represented  in  the  figure. 
This  must  be  done  so  slowly  as  to  keep  a  moderate  and  uni- 
form flow  of  gas  through  the  potash  solution.     When  the 
whole  tube  is  ignited,  and  gas  no  longer  escapes,  the  closed 
end  of  the  combustion  tube  is  broken  off,  and  a  little  air 
drawn  through  the  apparatus  to  remove  all  the  remaining 
products  of  combustion.     The  tubes  are  then  detached,  and 
from  the  increase  of  weight  in  the  chlorid  of  calcium  tube, 
the  amount  of  water,  and  thence  that  of  hydrogen,  is  deduced. 
The  carbon  is  determined  from  the  increase  in  weight  of  the 
potash  bulb  tube,  by  a  simple  calculation. 

670.  Volatile  liquids   are    analyzed  by  enclosing   them 
in  a  narrow-necked  bulb  of  thin  glass.     The  weight  of  the 
empty  tube  is  first  ascertained ;  the  liquid  is  introduced, 
the  neck  sealed,  the  weight  being  again  ascertained,  and 
the  difference  gives  the  weight  of  the 

substance.  The  neck  of  the  bulb  is 
then  broken  by  a  file  mark  at  cr,  ffig. 
400,)  dropped  into  'the  closed  end  of 
the  combustion  tube,  and  covered  with 
oxyd  of  copper,  which  should  nearly  fill 
the  tube.  When  this  is  heated  to  red- 
ness, a  gentle  heat  applied  to  the  por-  f< 
tion  of  the  combustion  tube  containing 
the  volatile  fluid,  sends  it  in  vapor  over 
the  ignited  oxyd,  completely  burning  it.  Flg>  40°* 

The  products  of  its  combustion  are  estimated  as  before. 


394  ORGANIC   CHEMISTRY. 

671.  Fatty  bodies,  and  others  which  contain  much  carbon 
and  a  small  quantity  of  hydrogen,  are  more  perfectly  burned 
by  employing  chromate  of  lead  instead  of  copper.     This  sub- 
stance does  not  readily  attract  moisture  from  the  atmosphere, 
like  oxyd  of  copper,  and  is  consequently  better  when  the  hy- 
drogen is  to  be  determined  accurately.    The  chromate  of  lead 
is  prepared  for  use  by  heating  it  until  it  begins  to  fuse,  and 
when  cool  reducing  it  to  powder. 

672.  When  nitrogen  is  a  constituent  of  organic  bodies, 
it  is  determined  by  placing  in  one  end  of  the  combustion 
tube  about  three  inches  of  carbonate  of  copper,  secured  in 
its  place  by  a  plug  of  asbestus ;  and  then  the  nitrogenous 
body  is  introduced,  mixed  with  oxyd  of  copper.     The  re- 
maining space  in  the  combustion  tube  is  filled  with  turnings 
of  metallic  copper.     The  air  is  then  withdrawn  by  an  air- 
pump,  and  a  gentle  heat  applied  to  the  carbonate  of  copper, 
which  evolves  carbonic  acid,  and  drives  out  all  remaining 
traces  of  common  air.     The  tube  is  now  heated  as  usual, 
and  the  gases  evolved  are  collected  in  a  graduated  air-jar, 
over  mercury.     When  the  combustion  is  finished,  heat  is 
again  applied  to  the  carbonate  of  copper,  and  another  portion 
of  carbonic  acid  expelled,  which  drives  out  all  the  nitrogen 
from  the  tube.     The  use  of  the  copper  turnings  is  to  decom- 
pose any  traces  of  nitric  oxyd  which  may  be  formed  in  the 
process.     The  carbonic  acid  is  removed  from  the  air-jar  by 
a  strong  solution  of  potash,  and  pure  nitrogen  remains, 
which  is  measured  with  the  usual  precautions,  and  from  its 
volume  the  weight  is  easily  determined. 

673.  Another  and  a  preferable  mode  of  determining  nitro- 
gen, is  that  of  Will  and  Varrentrapp,  which  is  founded  on  the 
fact  that  when  a  body  containing  nitrogen  is  heated  with  an 
excess  of  caustic  potash,  or  soda,  all  the  nitrogen  is  evolved 
in  the  form  of  ammonia,  and  may  be  thus  estimated,  by  con- 
ducting it  into  hydrochloric  acid,  and  forming,  with  chlorid 
of  platinum,  the  double  chlorid  of  platinum  and  ammonium. 

674.  Chlorine  is  determined  in  the  analysis  of  organic 
compounds,  by  passing  the  vapor  over  quicklime  heated  to 
redness  in  a  combustion  tube;  chlorid  of  calcium  is  formed, 
which  is  afterward  dissolved   in  water,  and   the   chlorine 
precipitated  by  nitrate  of  silver.     From  the  weight  of  the 
chlorid  of  silver,  the  amount  of  chlorine  is  calculated. 

675.  Sulphur  is  a  rare  constituted  of  organic  compounds. 
tts  presence  is  detected  by  fusion  with  nitre  and  carbonate 


DENSITY   OF   VAPORS. 


395 


of  soda,  or  by  digestion  with  nitric  acid.  Sulphuric  acid  is 
thus  formed,  and  is  precipitated  as  sulphate  of  baryta,  from 
the  weight  of  which  that  of  the  sulphur  is  determined.  In 
the  analysis  with  oxyd  of  copper,  a  small  tube  of  peroxyd 
of  lead  is  introduced  between  the  chlorid  of  calcium  tube 
ind  the  potash  apparatus,  to  absorb  the  sulphurous  acid 
rrhich  is  evolved. 

Density  of  Vapors. 

676.  The  determination  of  the  destiny  of  vapors  is  of 
great  importance ;  in  the  case  of  some  volatile  organic  com- 
pounds which  form  no  combinations  with  other  substances,  it 
is  the  only  means  of  ascertaining  their  constitution  and  equi- 
valent. The  process  is  very  simple,  and  the  method  employed 
in  the  case  of  gases  has  been  already  described,  (49.)  When 
the  substance  is  a  liquid  or  solid,  it  is  introduced  into  a  narrow- 
necked  glass  globe,  of  the  form  represented  in  fig.  401,  the 
weight  of  which  is  carefully  ascertained.  The 
globe  is  held  by  means  of  a  handle  firmly 
attached  by  a  wire,  beneath  the  surface  of  an 
oil  or  water-bath,  and  then  heated  to  some 
degrees  above  the  boiling-point  of  the  sub- 
stance. When  this  is  all  volatilized  and  the 
globe  is  filled  with  the  vapor,  the  open  and 
projecting  end  of  the  globe's  neck  is  sealed 
by  the  flame  of  a  spirit-lamp  :  at  the  same 
time  the  temperature  of  the  bath  is  noted. 
When  the  globe  is  cooled  it  is  again  weighed, 
and  the  end  of  the  neck  broken  off  beneath 
the  surface  of  mercury,  which  rushes  up  and 
fills  the  empty  vessel.  The  mercury  is  then  ^. 
carefully  measured.  The  capacity  of  the 
vessel  and  its  weight  being  thus  ascertained,  we  can  find 
the  weight  of  a  volume  of  vapor  at  the  observed  tempera- 
ture, and  by  an  easy  calculation  can  determine  what  would 


be  its  volume  at  the  ordinary  temperature,  (88:)  its  weight 

he  same  volume  of 
specific  gravity  required. 


»/  A  /    \  /  o 

compared  with  that  of  the  same  volume  of  air  gives  the 


677.  It  is  proposed,  before  commencing  the  study  of  those 
bodies  of  the  carbon  series  which  we  have  included  under 
the  head  of  Organic  Chemistry,  to  consider  briefly  the  prin- 
cipal products  of  the  ultimate  decomposition  of  this  class 
of  substances.  These  are  water,  ammonia,  and  carbonio 


396  ORGANIC   CHEMISTRY. 

acid  gas.  The  latter  only  strictly  comes  within  our  limits, 
and  all  of  them  have  been  described  in  the  first  part  of  this 
work ;  but  we  shall  bring  them  up  again  to  illustrate  certain 
laws  of  substitution,  which  will  help  to  explain  the  history 
of  the  more  complex  organic  compounds. 

We  shall  then  treat  of  starch  and  sugar,  and  some  other 
bodies  of  high  equivalents,  whose  history  is  comparatively 
simple,  and  proceed  to  the  products  of  their  decomposition 
by  fermentation  and  other  means,  among  which  are  different 
alcohols  and  acids. 

Water. 

678.  In  the  first  part  of  this  volume,  water  has  been  de- 
scribed as  having  the  formula  HO,  and  as  composed  of  two 
volumes  of  hydrogen  and  one  of  oxygen,  condensed  into  two 
volumes  of  vapor  of  water ;  we  have  already  given  the  rea- 
sons which  lead  us  to  adopt  four  volumes  as  its  equivalent, 
and  to  write  its  formula  Ha03. 

We  shall  now  speak  of  the  products  of  substitution  de- 
rived from  water.  If  the  oxygen  be  replaced  by  sulphur 
we  have  sulphuretted  hydrogen :  the  selenium  and  tellu- 
rium compounds  have  a  similar  composition.  One  or  both 
atoms  of  the  hydrogen  may  be  replaced  by  a  metal.  Hy- 
drate of  potash  KO.HO  is  water  in  which  one  equivalent 
of  H  is  replaced  by  potassium :  it  is  (KH)03,  and  anhy- 
drous potash  will  be  K203.  The  hydrated  oxyds  result  from 
the  replacement  of  one  equivalent  of  hydrogen  by  a  metal, 
while  in  the  anhydrous  oxyds  both  are  thus  replaced. 
Water  thus  resembles  a  bibasic  acid,  and  the  hydrated 
oxyds  may  be  compared  to  acid  salts,  while  the  anhydrous 
oxyds  are  like  neutral  salts. 

679.  The    so-called   suboxyds   are   illustrations   of   the 
change  of  equivalent  upon  which  we  have  insisted.     The 
red  oxyd  of  copper  is  Cu20,  or  rather  Cu402,  but  copper 
here  unites  in  twice  its  ordinary  equivalent  weight,  and  in 
this  form,  which  we  may  designate  as  cuprosum,  with  the 
symbol  cu,  is  strictly  equivalent  to  H  and  to  Cu,  so  that  tho 
red  oxyd  is  cu202.     The  peroxyds,  like  those  of  hydrogen 
or  barium,  may  be  either  oxyds  which  have  combined  with 
an  additional  amount  of  oxygen,  and  thus  increased  their 
equivalent  weight,  being  H204  and  Ba304,  or  they  may  be 
regarded  as  sustaining  to  the  ordinary  oxyds  the  same  re- 
lation that  the  black  oxyd  of  copper  does  to  the  red  oxyd, 


AMMONIA.  897 

being  compounds  in  which  barium  and  hydrogen  unite  in 
one-half  their  ordinary  equivalent :  thus,  (Bai)303,  &c.  The 
same  views  apply  to  the  persulphuret  of  hydrogen  and 
other  persulphurets.  From  the  volumes  of  the  correspond- 
ing bodies  of  the  carbon  series,  the  first  view  is  probably  the 
true  one. 

680.  We  have  shown  that  in  the  group  H3,  chlorine  may 
replace  H  to  form  chlorohydric  acid,  and  we  may  here  refer 
to  an  example  in  which  an  atom  of  the  hydrogen  is  replaced 
by  a  metal.   It  is  a  product  of  the  action  of  hypo-phosphorous 
acid  upon  a  salt  of  copper,  and  is  a  yellow  powder  contain- 
ing Cu2H,  which  corresponds  to  cuH.     Chlorohydric  acid 
dissolves  it  with  the  evolution  of  hydrogen  and  the  forma- 
tion of  a  chlorid  of  duprosum,  cuH-f-HCl  — cuCl-f-HH, 
the  hydrogen  of  both  being  evolved. 

It  has  already  been  remarked  that  there  are  examples  of 
bodies  in  which  all  of  the  hydrogen  may  be  replaced  either 
by  chlorine  or  by  a  metal,  and  water  is  such  a  body;  hydrated 
hypochlorous  acid  CIO, HO  is  (ClH)Oa,  or  water  in  which 
Cl  replaces  H :  the  second  equivalent  of  hydrogen  may  be 
replaced  by  a  metal  to  form  a  hypochlorite,  as  in  C10.KO, 
which  is  (C1K)03.  But  this  second  equivalent  may  also  be 
replaced  by  chlorine,  and  we  have  the  so-called  anhydrous 
hypochlorous  acid,  which  is  C1302,  or  water  in  which  chlo- 
rine has  been  substituted  for  the  whole  of  the  hydrogen. 

Ammonia. 

681.  Ammonia  is  composed  of  six  volumes  of  hydrogen 
and  two  of  nitrogen  (0  being  represented  by  one  volume,) 
condensed  to  one-half,  or  to  four  volumes :  its  formula  is 
then  NH3.     Its  properties  have  already  been  described,  and 
we  have  only  to  notice  some  of  its  derivatives.    Like  water, 
the  whole  of  its  hydrogen  may  be  replaced  either  by  chlo- 
rine or  by  a  metal.     The  direct  action  of  chlorine  decom- 
poses it;  the  hydrogen  forms  hydrochloric  acid,  and  the 
nitrogen  is  set  free  in  the  form  of  gas ;  but  with  a  solution 
of  a  salt  of  ammonia,  like  the  muriate  or  sal-ammonia,  the 
action  is  different ;  the  chlorine  is  slowly  absorbed  and  a 
heavy  yellow  oil  separates,  which  is  a  most  dangerous  com- 
pound, exploding  with  great  violence  by  a  gentle  heat,  by 
the  contact  of  phosphorus,  fat  oils,  and  many  other  sub- 
stances.    It  is  composed  of  NC13,  and  by  the  explosion  is 
resolved  into  these  elements.    The  name  of  chlorid  ofnitto- 


398  ORGANIC   CHEMISTRY. 

gen  has  been  given  to  it,  but  it  is  ammonia  in  which  the 
hydrogen  has  been  replaced  by  chlorine,  and  may  be  called 
trichloric  ammonia.  The  action  of  iodine  upon  ammonia  is 
more  moderate  than  that  of  chlorine  :  if  it  is  triturated  with 
a  solution  of  ammonia  or  mixed  in  an  alcoholic  solution,  a 
black  powder  is  obtained  which  explodes  when  dry  by  the 
slightest  friction,  but  less  violently  than  the  chlorid.  Its 
composition  is  NI2H,  and  it  is  therefore  liniodic  ammonia. 
The  chlorine  compound  is  indifferent  to  acids,  but  the 
iodic  species  still  exhibits  feebly  basic  properties :  it  is 
dissolved  by  dilute  acids  and  precipitated  again  by  a  solu- 
tion of  potash. 

682.  When  potassium  is  heated  in  ammoniacal  gas,  one 
equivalent  of  hydrogen  is  displaced,  and  an  olive-green  com- 
pound is  obtained,  which  is  N(H2K),  and  is  decomposed  by 
water  into,  hydrate  of  potash  and  ammonia  N(H3K)-{-H303 
=(HK)02-f-NH3.     When  ammonia  is  passed  over  heated 
oxyd  of  copper,  water  is  formed,  and  a  compound  which  con- 
tains Cu6N.    It  corresponds  to  the  red  oxyd  of  copper,  or  oxyd 
of  cuprosum  cu202,  and  is  Ncu3,  or  ammonia  in  which  all  the 
hydrogen  has  been  replaced  by  cuprosum.     It  is  formed  at 
a  temperature  of  480°  F.,  and  is  decomposed  into  its  ele- 
ments with  evolution  of  light  at  540°  F. 

683.  The  salts  of  ammonia  next  claim  our  notice.    Their 
characters  and  preparation,  and  the  theory  of  ammonium 
have  already  been  described,  (518.)     The  mode  of  their 
formation  is  different  from  that  of  ordinary  salts  of  metals  : 
these,  we  have  shown,  whether  the  metals  or  their  oxyds 
are  employed,  are  produced  by  an  equivalent  substitution 
with  the  elimination  of  hydrogen  or  water,  while  ammonia 
and  the  acids  unite  directly  to  form  salts,  without  the  pro- 
duction of  any  second  body.      Thus  ammonia  and  chlo- 
rohydric    acid    NH3-j-HCl    yield    sal-ammoniac    NH4C1; 
and  sulphuric  acid,  which  is  bibasic  and  must  be  written 
2S03.H202=S2H208,  fixes  directly  2NH3  to  form  sulphate 
of  ammonia.     But  these  salts,  notwithstanding  their  differ- 
ent mode  of  formation,  are  closely  analogous  to  the  salts 
of  potassium  and  even  isomorphous  with  them ;  and  while 
chlorid  of  potassium  is  KC1,  the  NH4  in  sal-ammoniac  i& 
perfectly  similar  in  its  relations  to  K ;  and  hence  sal-ammo- 
niac is  often  regarded,  not  as  the  hydrochlorate  of  ammonia 
NH3.IJC1,  but  as  the  chlorid  of  a  quasi-metal,  ammonium, 
which  unites  with  Cl  like  potassium,  and,  like  this  metal, 


AMMONIA.  899 

may  even  form  an  amalgam  with  mercury ;  for  (NII4)Hg 
evidently  corresponds  to  KHg,  and  Zntlg.  Ammonium,NH4, 
is  then  a  group  which,  although  it  cannot  be  isolated,  may 
replace  hydrogen,  and  is  equivalent  to  it.  The  neutral 
sulphate  of  ammonia  is  S8(NH4)aOs,  as  sulphate  of  potash  is 
S3(K3)08,  and  the  acid  sulphate  S3(H.NH4)08,  corresponding 
to  Sa(HK)08.  The  group  NH4  may  be  represented  by  the 
symbol  Am. 

684.  The  compound  corresponding  to  a  metallic  oxyd  in 
which  NH4  replaces  H,  like  (KH)02,  probably  exists  in  the 
aqueous  solution  of  ammonia :   it  will  be  (NH4.  H)02  or 
(AmH)02;  but  the  ammonia  is  readily  evolved  by  heat,  the 
compound  being  like  some  salts  of  ammonia,  very  unstable. 
We  shall  see  hereafter  that  there  are  homologues  of  ammo- 
nia which  form  more  fixed  combinations.     A  compound  of 
(NH4)302,  or  Am202,  corresponding  to  an  anhydrous  oxyd, 
is  also  possible ;  like  oxyd  of  zinc,  (Zn203,)  it  would  evolve 
an  equivalent  of  water  in  combining  with  an  acid. 

685.  In  the  same  way  that  ammonia  combines  directly 
with  acids  it  may  unite  with  metallic  salts ;  for  example, 
with   chlorid    of    copper    CuCl-f-NH3  =  (NH3Cu)Cl,   and 
with  sulphate  of  silver  S3Ag2Os-f-2NH3=S2(NH3Ag)203: 
in   these   compounds  one  equivalent   of  hydrogen   in   the 
ammonia  is  replaced  by  copper  and  silver,  and  the  groups 
may  be  designated  cuprammonium  and  argentammonium. 
The  white  precipitate  of  mercury  obtained  by  adding  am- 
monia to  a  solution  of  chlorid  of  mercury  is  a  body  of  this 
class,  and  is  represented  by  (NH2Hg3)Cl :   when  this  is 
boiled  in  a  solution  of  sal-ammoniac,  another  compound  is 
obtained,  which  is  (NH3Hg)Cl.     Here  one  and  two  equiva- 
lents of  hydrogen  are  replaced  by  mercury. 

With  the  chlorid  of  platinum  a  similar  chlorid  is  obtain- 
ed, which  is  known  as  the  green  salt  of  Magnus,  and  is 
(NH3Pt)Cl.  But  the  group  NH4  may  replace  an  equivalent 
of  H  in  the  last,  and  we  have  a  salt  described  by  Gros  and 
Ileiset,  which  is  N(AmH2Pt)Cl  or  (N3H6Pt)Cl.  Still  another 
one  has  an  equivalent  of  hydrogen  replaced  by  01,  and  is 
(N3H5ClPt)Cl.  All  of  these  correspond  to  chlorid  of  ammo- 
nium, and  it  will  be  observed  that  the  sum  of  their  atoms 
is  always  divisible  by  two.  They  combine  with  the  oxygen 
acids  like  ammonia,  and  their  sulphates,  when  decomposed  by- 
baryta,  give  the  hydrated  oxyds  corresponding  to  (KH)Oi; 


400  ORGANIC   CHEMISTRY. 

and,  like  it,  caustic  and  alkaline.     Cobalt  and  some  other 
metals  yields  analogous  compounds. 

686.  The  decomposition  of  ammoniacal  salts  to  form  water 
and  amids  has  already  been  alluded  to,  (654.)     An  ammo- 
niacal salt  eliminates  one  equivalent  of  water  for  each  equi- 
valent of  ammonia  which  it  contains,  and  the  salt,  if  neutral, 
yields  a  neutral  amid ;  but  if  the  salt  is  acid,  that  is,  if  a 
bibasic  acid  has  combined  with  one  equivalent  of  ammonia, 
and  has  still  an  atom  of  hydrogen  replaceable  by  a  metal, 
this  is  preserved  in  the  amid,  which  is  then  a  monobasic  acid. 
These  compounds  are  often  directly  formed  by  the  action  of 
heat  upon  the  several  salts,  and   sometimes  by  distilling 
them  with  anhydrous  phosphoric  acid,  which  combines  with 
the  water.     Amids  may  sometimes  lose  the  elements  of 
another  equivalent  of  water,  and  form  a  class  of  bodies 
known  as  anhydrid  amids,  or  nitryls.    Acetate  of  ammonia 
C4H404+NH3=C4H7N04— H202  =  C4H5N02,  or  acetamid, 
from  which  if  H203  be  again  abstracted,  there  remains 
acetonitryl  C4H3N. 

687.  Nitrous  oxyd,  which  is  NO,  or  rather  N202,  is  formed 
from  nitrate  of  ammonia  NH06.NH3,  by  the  abstraction  of 
2H202,  and  is  a  true  nitryl.    Like  all  the  other  bodies  of  this 
class,  it  can  reassume  the  elements  of  water  and  regenerate 
the  acid  and  ammonia ;  when  passed  over  heated  hydrate  of 
potash,  a  nitrate  is  formed,  ammonia  escaping. 

Phosphoric  acid  forms  not  less  than  three  anhydrid  amids, 
corresponding  to  different  salts  of  the  different  modifications 
of  the  acid.  They  are  all  white  insoluble  powders,  which, 
under  the  influence  of  strong  acids  or  alkalies,  yield  phos- 
phoric acid  and  ammonia.  The  one  corresponding  to  nitrous 
oxyd  is  (PN)Oa=P05.NH4p-2HaOa. 

The  points  of  interest  with  regard  to  the  amids  of  the 
organic  acids  will  be  considered  in  their  proper  places. 

Carbonic  Acid. 

688.  This  compound  has  already  been  described,  but  we 
again  refer  to  it  to  speak  of  its  equivalent,  which,  to  corre- 
spond to  those  adopted  for  organic  substances,  must  be  writ- 
ten C304  in  its  anhydrous  state.     The  gas  fixes  H202  when 
it  takes  the  acid  form ;  and  carbonic  acid,  such  as  it  exists 
in  solution,  is  consequently  C2H206,  in  which  one  or  both 
equivalents  of  hydrogen  may  be  replaced  by  a  metal,  form- 


SUGAR,    STARCH,    ETC.  401 

ing  neutral  and  acid  carbonates,  or  bicarbonates,  as  they  are 
often  called.  . 

Carbonic  acid  is  very  readily  separated  from  its  aqueous 
solution,  or  decomposed  into  carbonic  acid  gas  and  water,  in 
which  it  differs  from  more  fixed  bibasic  acids,  which  some- 
times require  a  high  temperature  to  effect  such  a  division. 

689.  Carbonic  oxyd,  which  we  write  Ca02,  is  interesting 
from  its  action  with  chlorine  in  the  formation  of  phosgene 
gas.  It  directly  fixes  2C1  to  form  C3C1303,  which  evidently 
corresponds  to  an  hydrogen  compound  C3H30.  This  group, 
of  which  phosgene  is  the  chlorinized  species,  is  the  prototype 
of  an  important  class  of  organic  compounds,  the  aldehydes 


SUGAR,  STARCH,  AND  ALLIED  SUBSTANCES. 

690.  Under  this  head  is  included  a  class  of  substances  of 
vegetable  origin,  which  agree  in  containing  carbon  with  oxy- 
gen and  hydrogen  in  the  proportions  which  form  water. 
When  soluble,  they  are  insipid,  or  have  a  sweet  taste,  and 
are  generally  nutritious.     They  are  not  volatile,  and  are 
readily  decomposed  by  heat  and  many  other  agents. 

691.  Sugars.  —  These  bodies  are  soluble  in  water,  have  a 
sweet  taste,  and  most  of  them  by  the  process  of  fermentation 
yield  alcohol  and  carbonic  acid. 

Cane  Sugar,  CMH3aOS3.  —  This  occurs  in  the  juices  of 
many  plants,  as  the  sugar-cane,  maple,  beet-root,  and  Indian 
corn.  It  is  obtained  by  evaporating  the  juice  to  a  syrup, 
when  the  sugar  crystallizes  in  grains  of  a  brownish  color, 
and  is  rendered  pure  and  white  by  redissolving  it,  and  filter- 
ing the  solution  through  animal  charcoal,  (337.)  By  the 
slow  evaporation  of  a  concentrated  solution,  it  is  obtained 
in  fine  transparent  crystals,  which  are  derived  from  an  oblique 
rhombic  prism  ;  in  this  state  it  constitutes  rock-candy.  It 
fuses  at  356°,  and  forms,  on  cooling,  a  vitreous  mass  well 
known  as  barley  sugar  :  this  gradually  becomes  opaque  and 
changes  into  a  mass  of  small  crystals  of  ordinary  sugar. 
Sugar  is  soluble  in  about  one-third  its  weight  of  water,  form- 
ing a  thick  syrup.  It  is  insoluble  in  pure  alcohol. 

692.  Grape  Sugar;  Glucose,  C^H^O^  -f  2H803.—  This 
sugar  is  found  in  the  grape  and  many  other  fruits,  and  in 
honey.    It  is  formed  when  cane  sugar  or  starch  is  boiled  with 
dilute  sulphuric  acid,  and  is  a  product  in  many  other  trans- 

26 


402  ORGANIC   CHEMISTRY. 

formations.  The  urine  in  the  disease  called  diabetes  meUituz 
contains  a  large  quantity  of  grape  sugar,  which  is  formed 
from  the  starch  and  similar  substances  taken  as  food. 

Grape  sugar  is  generally  obtained  as  a  white  granular 
mass,  which  requires  one  and  a  half  parts  of  cold  water  to 
dissolve  it :  it  is  less  sweet  to  the  taste  than  cane  sugar,  and 
about  two  and  a  half  times  as  much  are  required  to  give  an 
equal  sweetness  to  the  same  volume  of  water.  When  heated 
to  212°,  the  two  equivalents  of  water  are  expelled.  With 
sulphuric  acid,  grape  sugar  forms  a  coupled  acid,  the  sul- 
pbosaccharic.  It  forms  with  chlorid  of  sodium,  a  crystal- 
line compound,  which  is  C^H^O^-NaCl.!!,^.  The  water 
is  lost  by  heat.  If  a  solution  of  grape  sugar  is  mixed  with 
a  solution  of  potash,  and  then  with  a  little  sulphate  of  copper, 
the  liquid  becomes  dark,  and  soon  deposits  suboxyd  of  copper 
in  the  form  of  a  red  powder ;  cane  sugar  yields  no  precipi- 
tate until  the  solution  is  boiled.  This  test  enables  us  to  detect 
the  Yflflss  part  of  grape  sugar  in  a  liquid.  Honey  is  a  mix- 
ture of  crystallizable  grape  sugar,  with  an  uncrystallizable 
syrup  identical  with  it  in  composition. 

693.  Sugar  of  Milk;  Lactose,  CWH2?020+2H303.— This 
is  found  only  in  the  whey  of  milk,  and  is  obtained  by  evapo- 
rating it,  and  purifying  the  product  by  crystallization. 
Lactose  forms  semi-transparent  prisms,  soluble  in  six  parts 
of  cold  water,  and  two  and  a  half  of  boiling  water ;  it  is 
much  less  sweet  than  cane  or  grape  sugar.  By  a  heat  of 
212°  its  water  is  expelled ;  when  boiled  with  dilute  sulphuric 
acid,  it  combines  with  the  elements  of  two  equivalents  of 
water,  and  is  converted  into  grape  sugar. 

Mannite,  C13H140la. — This  substance  is  not  properly  a 
sugar,  as  it  does  not  contain  oxygen  and  hydrogen  in  the 
proportions  to  form  water,  and  is  not  susceptible  of  fermenta- 
tion. It  exists  in  the  juice  of  celery  and  many  sea-weeds, 
and  constitutes  the  principal  part  of  the  manna  of  the  shops, 
which  is  the  concreted  juice  of  a  species  of  ash-tree.  When 
this  is  dissolved  in  hot  alcohol,  mannite  is  deposited  oa 
cooling  in  delicate  silky  crystals,  which  are  sweet,  and  very 
soluble  in  water  and  alcohol. 

Mannite  dissolves  in  a  mixture  of  fuming  nitric  and  sul- 
phuric acids,  and  water  precipitates  from  the  mixture  a 
white  matter,  insoluble  in  water,  which  may  be  crystallized 
by  dissolving  in  hot  alcohol.  It  is  formed  by  the  fixation  of 
the  elements  of  nitric  acid  and  the  elimination  of  those  of 


VINOUS    FERMENTATION.  403 

water,  and  is  represented  by  C12H8N"(.03(i.  We  may  repre- 
sent N04  as  replacing  hydrogen,  and  designate  it  by  X 
The  new  compound,  which  is  called  nilro-mannite,  will  be 
then  C12HS(N04)6012  —  C13H8X6013.  This  mode  of  notation 
is  convenient,  but,  agreeably  to  the  views  laid  down  in  the 
introduction,  we  must  suppose  successive  substitutions,  in 
the  first  of  which  C13Ht4013 — H0a  replaces  H  in  nitric  acid 
NH06,  yielding  N(C13H13010)On  and  H30a;  this  product 
then  reacts  with  a  new  equivalent  of  nitric  acid,  and  so  on. 
From  the  large  portion  of  oxygen  which  it  contains,  nitro- 
mannite  is  very  combustible,  and  it  explodes  spontaneously 
when  struck  with  a  hammer. 

Products  of  the  Decomposition  of  the  Sugars. 

694.  The  Vinous  Fermentation. — When  the  juice  of  grapea 
or  other  fruits  containing  sugar  is  exposed  to  the  air,  a  pecu- 
liar decomposition  ensues,  in  which  the  sugar  is  resolved 
into  carbonic  acid  gas  and  alcohol.  A  solution  of  pure 
sugar  is  not  changed  by  exposure  to  the  air ;  but  if  there  is 
added  to  it  a  little  yeast,  or  the  juice  of  any  fruit  in  the  state 
of  fermentation,  decomposition  takes  place,  and  carbonic  acid 
and  alcohol  are  formed.  Many  substances  besides  yeast  will 
effect  this  change,  as  blood,  albumen,  or  flour  paste  in  a  state 
of  decomposition.  It  appears  that  the  influence  of  a  fer- 
ment depends  on  the  condition  rather  than  on  the  kind  of 
matter.  Any  nitrogenized  substance  capable  of  undergoing 
putrefaction  produces  the  same  effect,  and  we  are  to  attribute 
this  change  in  the  juice  of  fruits,  to  a  small  portion  of  albu- 
minous matter  present.  The  mode  in  which  these  substances 
act  is  not  understood,  but  it  is  supposed  that  when  in  a  state 
of  decomposition,  they  are  able  to  induce  a  similar  state  in 
other  substances  with  which  they  are  in  contact;  the  equi- 
librium of  the  atoms  in  the  compound  is  thus  disturbed,  and 
the  elements  arrange  themselves  in  new  forms. 
It  is  interesting  to  know  that  the  fermentation 
of  sugar  takes  place  only  in  immediate  contact 
with  the  ferment.  This  is  readily  shown,  as  in 
figure  402,  by  placing  a  solution  of  sugar  in  the 
bottle  A,  and  some  beer  yeast  in  the  tube 
ab}  the  lower  end  of  which  is  covered  with 
porous  paper.  The  sugar  solution  passes 
through  the  paper  into  the  tube,  where  an 
active  fermentation  is  set  up  with  an  abundant  Fig.  402. 


404  ORGANIC   CHEMISTRY. 

evolution  of  carbonic  acid.  Meanwhile  no  change  occurs  in 
the  solution  in  the  bottle,  which  may  be  preserved  unaltered 
for  any  length  of  time. 

G95.  The  act  of  fermentation  is  always  accompanied  by 
the  appearance  of  a  peculiar  microscopic  vegetation,  which 
is  formed  when  solutions  containing  albuminous  matters 
are  abandoned  to  putrefaction.  The  solution  becomes  tur- 
bid, and  a  gray  deposit  is  gradually  formed  in  it,  consisting 
of  ovoidal  bodies  variously  grouped,  whose  development  has 
been  carefully  studied  under  the  microscope.  Figures  403 
to  407  show  the  various  stages  of  this  fungus  growth.  The 


±  >*  C   -W3 

Fig.  403.     Fig.  40i.       Fig.  405.         Fig.  406.  Fig.  407. 

original  globule  (1)  A,  fig.  403,  in  about  six  hours  produces 
another,  (2,)  fig.  404,  13,  like  itself;  the  two  again  each 
germinate  a  third,  as  seen  at  3,  C  and  D,  fig.  405;  and  in 
like  manner  the  germination  proceeds,  as  in  E,  (4,)  fig.  406, 
until,  in  about  throe  days,  thirty  globules  are  formed  about 
the  original  cell.  The  development  then  ceases.  The  se- 
veral globules  are  coherent,  but  appear  to  be  distinct  and 
complete  in  themselves. 

696.  The  conversion  of  grape  sugar  into  alcohol  and  car- 
bonic acid  is  very  simple :  one  equivalent  of  dry  grape  sugar 
C^H^O.^  divides  so  as  to  form  four  equivalents  of  alcohol 
and  four  of  carbonic  acid  gas. 

4  equivalents  of  alcohol  4XC4HB02 =  C^II^O, 

4  "  of  carbonic  acid  gas  4  X  Ca04  =  Cg       0,, 


1          "          of  grape  sugar 


Grape  sugar  is  the  only  kind  which  is  capable  of  this  fer- 
mentation ;  and,  although  the  others  readily  yield  alcohol 
and  carbonic  acid,  it  is  found  that  the  first  effect  of  the  fer- 
ment is  to  transform  them  into  grape  sugar,  by  the  assimila- 
tion of  the  elements  of  water. 

697.  Weak  alcoholic  liquors  often  become  acid  when 
exposed  to  the  air,  from  oxydation  of  the  alcohol  and  the 
formation  of  acetic  acid  ;  but  this  acid  is  sometimes  directly 


LACTIC   ACID.  \C 

formed  from  the  decomposition  of  the  sugar,  independent  of 
the  action  of  the  air,  and  is  the  cause  of  the  souring  of  such 
wines  as  contain  considerable  sugar,  but  are  very  weak  in 
alcohol.  If  a  solution  of  sugar  is  mixed  with  cheese  curd 
and  exposed  for  some  weeks  to  a  temperature  of  about  68°  F., 
the  air  being  excluded,  it  becomes  acid,  and  a  portion  of  the 
sugar  is  converted  into  acetic  acid  C4H404.  An  equivalent 
of  grape  sugar  contains  the  elements  of  six  equivalents 
of  this  acid.  The  presence  of  cheese  curd  under  condi- 
tions modified  by  temperature  and  the  presence  of  earthy 
bases,  causes  other  fermentations  and  different  results.  At 
a  temperature  of  from  95°  to  104°  F.  the  products  are 
lactic  acid  C13H12012,  and  a  viscous  substance  analogous 
in  composition  to  sugar.  Such  a  decomposition  takes  place 
in  the  juices  of  beets  and  carrots  at  a  high  temperature,  and 
has  been  called  the  viscous  fermentation.  Mannite  some- 
times appears  as  a  secondary  product.  If  carbonate  of  lime 
is  added  to  saturate  the  lactic  acid  as  soon  as  formed,  the 
decomposition  proceeds  at  a  lower  temperature,  and  the 
lactate  of  lime  is  almost  the  only  product.  An  equivalent 
of  grape  sugar  C^II^O^.  breaks  up  into  two  equivalents  of 
lactic  acid  C12Hj3012. 

698.  The  action  of  the  curd  of  milk  in  a  more  advanced 
state  of  decomposition  gives  rise  to  the  vinous  fermentation  : 
milk  at  the   ordinary  temperature  becomes  sour  from  the 
conversion  of  its  sugar  into  lactic  acid,  but  when  kept  at 
about  100°  the  grape  sugar  at  first  formed  is  converted  into 
alcohol  and  carbonic  acid  gas.     In  this  way  the  Tartars  pre- 
pare a  spirit  from  mare's  milk;    an  elevated  temperature 
promotes  the  decomposition  of  the  curd  and  enables  it  to 
effect  this  transformation. 

699.  Lactic  Acid,  ClaH12013. — This  acid  may  be  obtained 
from  sour  milk,  but  is  more  easily  prepared  by  the  fermenta- 
tion of  sugar  with  caseine.    Fourteen  parts  of  cane  sugar  are 
dissolved  in  sixty  of  water ;  to  the  solution  is  then  added 
four  parts  of  the  curd  from  milk,  and  five  parts  of  chalk  to 
neutralize  the  acid  as  it  is  formed.     This  mixture  is  kept 
at  a  temperature  of  80°  to  95°  F.  for  eight  or  ten  days,  or 
until  it  becomes  a  crystalline  paste  of  lactate  of  lime.     This 
'ts  pressed  in  a  cloth,  dissolved  in  hot  water,  and  filtered ; 
the  solution  is  then  concentrated  by  evaporation.     On  cool- 
ing, it  deposits  the  salt  in  crystals,  which  may  be  purified 
by  recrystallization.      The  lactate  of  lime  may  be  V>CGIU- 


406  ORGANIC   CHEMISTRY. 

posed  by  the  careful  addition  of  oxalic  acid,  which  precipi- 
tates the  lime,  and  the  solution  of  lactic  acid  thus  obtained 
is  concentrated  by  evaporation,  and  puri6ed  by  solution  in 
«ther.  It  is  a  syrupy  liquid,  of  specific  gravity  1-215,  and 
is  strongly  acid  to  the  taste. 

700.  When  lactic  acid  is  heated  to  482°,  a  white  crystal- 
line substance  sublimes,  which  is  called  lactide:  it  is  derived 
from  the  acid  by  the  abstraction  of  the  elements  of  two  equi- 
valents of  water,  and  has  the  formula  C13IIS0S.     It  is  soluble 
in  alcohol,  but  scarcely  soluble  in  water  :  by  long  continued 
boiling  with  it,  however,  it  is  converted  into  lactic  acid. 
This  acid  is  bibasic,  and  its  salts  are  generally  soluble  and 
crystallizablc.     The  lactate  of  lime  C13H10Ca3013  crystallizes 
in  fine  prisms,  with  six  equivalents  of  water.     The  lactate 
of  zinc  is  obtained  by  decomposing  a  hot  concentrated  solu- 
tion of  lactate  of  lime  by  chlorid  of  zinc  :  the  salt  crystallizes 
in  cooling  in  beautiful  colorless  prisms.     The  lactate  of  iron 
CiaH10FcaOia  is  sparingly  soluble  in  cold  water,  and  may  be 
prepared  by  a  similar  process :  it  is  employed  in  medicine. 
A  double  lactate  of  lime  and  potash,  and  acid  lactates  of  lime 
and  baryta  have  been  obtained ;  the  latter  is  Cia(H11Ba)0ls. 
If  the  crystalline  paste  of  caseine  and  lactate  of  lime  is  kept 
for  some  time  at  a  temperature  of  about  95°,  the  salt  gradually 
redissolves,  hydrogen  and  carbonic  acid  gases  escape,  and 
when,   after  a  few  weeks,  this  new  fermentation  has  sub- 
sided, there  remains  only  a  solution  of  the   lime   salt  of  a 
new  acid,  butyric  acid,  C8HS04.  In  this  butyric  fermentation, 
the  lactic  acid  is  decomposed  into  carbonic  acid,  hydrogen 

•and  the  new  acid,  C13HI3013  =  2C304  +  2H3+C8H804. 

701.  Under  certain  circumstances  not  well  understood, 
there  appears  as  an  accessory  product  to  the  vinous  ferment- 
ation, an  oily  liquid,  which  is  homologous  with  alcohol  and 
has  been  named  amylol.    It  is  represented  by  C10H1303,  and 
is  supposed  to  be   formed  from   sugar  by  a  process  which 
may  be  called  the  amylic  fermentation,  in  which,  as  in  the 
butyric,  hydrogen  and  carbonic  acid  will  be  disengaged. 

The  action  of  dilute  nitric  acid  with  cane  or  grape  sugar 
yields  saccharic  acid  C^H^O^,  which  is  bibasic :  strong 
nitric  acid  converts  sugar  into  oxalic  acid,  and  chromic  acid 
into  formic  acid.  All  of  these  derivatives  will  be  described  in 
their  proper  places. 

702.  When  sugar  is  added  to  a  concentrated  solution  of 
three  times  its  weight  of  hydrate  of  potash,  and  heated,  the 


STARCH.  407 

mixture  becomes  brown,  and  hydrogen  gas  is  evolved.  When 
the  action  ceases  and  the  mass  is  cooled,  dissolved  in  water> 
and  distilled  with  dilute  sulphuric  acid,  it  yields  formic  and 
acetic  acids,  with  a  new  acid,  the  metacetonic,  which  is 
obtained  as  a  volatile  liquid,  with  a  pungent  acid  odor.  It 
is  monobasic,  and  has  the  formula  C6H604. 

A  mixture  of  sugar  and  quicklime,  when  distilled,  affords 
acetone  and  an  oily  liquid  called  metacetone  which  yields 
metacetonic  acid  when  distilled  with  a  mixture  of  bichromate 
of  potash  and  sulphuric  acid.  Mannite,  starch,  and  gum 
afford  the  same  results  with  hydrate  of  potash  and  lime. 

703.  Gum,  C^H^O,^. — This  substance  is  best  known  in 
gum  arable :  the  gums  which  exude  from  the  cherry  and 
plum,  the  mucilage  of  flaxseed,  and  of  many  other  plants, 
are  identical  with  it.     Gum  is  soluble  in  water,  and  forms  a 
viscid  solution,  from  which  alcohol  precipitates  it  unchanged. 

When  boiled  with  dilute  sulphuric  acid,  it  is  converted 
into  grape  sugar.  With  nitric  acid,  gum  and  lactose  yield 
the  rnucic  acid,  which  distinguishes  them  from  all  the  other 
bodies  of  this  class.  The  mucic  acid  is  a  white  crystalline 
powder,  which  is  sparingly  soluble  in  water :  it  is  bibasic, 
and  is  represented  by  the  formula  C13H10016.  It  is  conse- 
quently metameric  with  the  saccharic  acid,  although  quite 
different  in  its  properties. 

704.  The  pectic  acid,  which   is  extracted  from   many 
fruits,  appears  to  be  nothing  but  a  modified  form  of  gum, 
and  yields  grape  sugar  with  dilute  acids.     It  combines  with 
lime  and  some  other  bases  to  form  compounds,  which  have 
been  described  as  pectates.     Both  gum  and  sugar  have  also 
the  property  of  exchanging  one  or  two  equivalents  of  hy- 
drogen for  lead,  barium,  or  calcium,  to  form  similar  com- 
binations. 

705.  Starch,  C^H^O^. — This  substance  exists  in  a  great 
variety  of  vegetables.     It  is  found  in  all  the  cereal  grains, 
in  the  roots  and  tubers  of  many  plants,  as  the  potato,  and 
in  the  bark  and  pith  of  various  trees.     It  is  obtained  by 
bruising  wheat  and  washing  it  in  cold  water,  which  holds  the 
starch  in  suspension,  and  deposits  it  on  standing.     Potatoes 
furnish  a  large  portion  of  starch  by  a  similar  process.     The 
substances  known  as  arrow-root,  salep,  sago,  and  tapioca, 
are  varieties  of  starch,  obtained  from  different  plants,  and 
sometimes  altered  by  the  heat  employed  in  drying. 

When  examined  by  the  naked  eye  it  is  a  white  shining 


408 


ORGANIC    CHEMISTRY. 


powder,  but  under  the  micro- 
scope is  seen  to  consist  of  irregu 
lar  grains,  which  have  a  rounded 
outline,  and  are  composed  of 
concentric  layers,  covered  with 
an  external  membrane.  The 
diameter  of  the  grains  of  potato 
starch  is  about  2^D  of  an  inch. 
Starch  is  insoluble  in  cold 
water,  but  if  the  mixture  is 
heated,  the  globules  swell,  burst 
their  envelopes,  and  form  a 
transparent  jelly,  which  is  cha- 
racterized by  producing  a  deep  blue  color  with  a  solution 
of  iodine. 

When  the  solution  of  starch  is  mixed  with  a  little  acid,  or 
an  infusion  of  malt,  and  gently  heated,  it  becomes  very  fluid, 
and  is  changed  into  dextrine.*  This  has  the  same  com- 
position as  starch,  but  is  very  soluble  in  cold  water,  and  is 
not  colored  blue  by  iodine.  If  starch  is  heated  to  300°  or 
400°,  it  is  rendered  soluble  in  water,  and  possesses  all  the 
properties  of  dextrine.  In  this  state  it  is  used  in  the  arts  as 
a  substitute  for  gum,  under  the  names  of  British  yum  and 
Iciocomt'.  When  dextrine  is  boiled  for  some  time  with 
dilute  sulphuric  acid,  it  is  converted  into  grape  sugar.  It 
has  been  mentioned  that  grape  sugar  i.s  formed  in  this  way 
from  starch;  but  its  formation  is  always  preceded  by  that 
of  dextrine.  One  part  of  starch  may  he  dissolved  in  foui 
parts  of  water,  with  about  one-twentieth  of  sulphuric  acid, 
and  the  mixture  boiled  for  thirty-six  or  forty  hours.  The 
liquid  is  then  mixed  with  chalk  to  separate  the  acid,  and  by 
evaporation  and  cooling  affords  pure  grape  sugar.  Oxalic 
acid  may  be  substituted  for  the  sulphuric,  with  the  same 
result.  Starch  sugar  is  extensively  manufactured  in  Europe, 
and  is  often  used  to  adulterate  cane  sugar.  In  this  process 
the  starch  combines  with  the  elements  of  two  equivalents  of 
water,  Ca4Hso020-j-2HaOs=CS4HwO,M :  the  acid  is  obtained 
at  the  end  of  the  process  quite  unaltered,  and  one  part  of 
acid  will  saccharify  one  hundred  of  starch  by  long  continued 
boiling.  Starch  or  dextrine  unites  with  sulphuric  acid  to 

#So  named,  because  when  a  beam  of  polarized  light  is  passed  through 
the  solution,  it  causes  the  plane  of  polarization  to  deviate  to  the  riyht 
hand. 


WOODY    FIBRE. 


409 


form  a  coupled  acid;  and  it  is  probable  that  this  is  first 
formed  and  then  destroyed  by  boiling :  at  the  moment  of 
decomposition,  the  liberated  dextrine  takes  up  the  elements 
of  water  necessary  for  the  formation  of  sugar.  A  small 
portion  of  the  coupled  acid  is  always  found  in  the  solution. 

706.  The  action  of  an  infusion  of  malt  upon  sugar  is 
peculiar :    this    substance    is   prepared    from    barley,   by 
moistening  the  grain  with  water,  and  exposing  it  to  a  gentle 
heat  till  germination  takes  place,  when  it  is  dried  in  an  oven 
at  such  a  temperature  as  to  destroy  its  vitality.     The  grain 
now  contains  a  portion  of  starch  sugar,  and  a  small  portion 
of  a  substance  called  diastase*  to  which  its  peculiar  proper- 
ties are  due.     It  is  precipitated  by  alcohol  from  a  concen- 
trated infusion  of  malt,  as  a  white  flaky  substance,  which 
contains  nitrogen,  and  is  very  prone  to  decomposition.  When 
a  little  diastase  is  added  to  a  mixture  of  starch  and  water, 
at  a  temperature  of  from  130°  to  140°,  the  starch  is  soon 
converted  into  dextrine,  and  in  a  few  hours  into  grape  sugar. 
The  action  of  an  infusion  of  malt  is  due  solely  to  the  presence 
of  a  minute  portion  of  this  substance,  one  part  of  which  will 
convert  two  thousand  parts  of  starch  into  sugar.     This  effect 
appears  to  be  due  to  a  peculiar  state  of  the  diastase,  which  is 
a  portion  of  the  azotized  matter  of  the  grain  in  a  modified 
form,  and  is  analogous  to  the  ferments,  already  alluded  to. 

707.  Woody  Filrc;  Cellulose,  C24H30020.— This  substance 
is  the  solid  insoluble  part  of  vege- 
tables, and  remains  when  water, 

alcohol,  ether,  dilute  acids,  and  al- 
kalies have  extracted  from  wood 
all  its  soluble  portions.  It  is 
nearly  pure  in  cotton,  paper  or  old 
linen.  The  tissue  of  vegetables 
is  formed  principally  of  cellu- 
lose. The  cellular  tissue  is  seen 
almost  pure,  constituting  the  cell 
walls  of  young  plants.  These  cells 
arc  sometimes  spherical,  or  rounded 
in  form.  In  other  cases  the 
woody  tissue  forms  oblong  cells, 
communicating  by  their  extre*ni-  Fig.  409. 


#From  the   Greek   diistemi,  to   separate,  because  it  separates    the 
insoluble  envelopes  of  the  starch  globules. 


410 


ORGANIC   CHEMISTRY. 


ties,  as  seen  in  figure  409,  which  is  a  section  of  aspara- 
gus, and  also  in  figure  410,  which  shows  a  fibre  of  flax 
much  magnified.  The  cellulose  in  this  form  receives 
Jie  name  of  vascular  tissue.  In  the  course  of  time  the  walla 
of  the  cells  become  lined  with  an  incrusting  matter,  which 
grows  thicker  with  the  age  of  the  plant,  finally  leaving 

only  minute 
pores  or  con- 
duits for  the 
circulation  of 
the  sap.  This 

incrusting  matter  which  forms  a  part  of  ordinary  wood,  is 
named  lignin.  It  is  chemically . different  from  cellulose, 
but  has  been  little  studied.  Figure  411  shows  the  structure 
of  wood  as  seen  in  the  transverse  section  of  a  piece  of  oak, 
under  the  microscope.  The  black  spaces  are  the  ducts, 

for  the  circulation  of  the 
sap,  of  which  a  a  a  are  re- 
markable examples.  The 
white  lines  mark  the  outline 
and  comparative  thickness 
of  the  original  cells,  such  as 
are  seen  in  the  vertical  sec- 
tion of  asparagus,  fig.  409. 
These  have  been  filled  with 
lignin,  which  is  more  dense 
and  hard  near  the  centre  of 
the  tree  than  at  the  exterior. 
The  albuminous  matters, 
Fig.  411.  which  are  the  principal 

cause  of  the  decay  of  wood,  are  also  more  abundant  in  the 
outer  than  in  the  inner  cells.  The  coloring  and  resinous 
matters  are  deposited  with  the  incrusting  material. 

Cellulose  is  identical  in  composition  with  starch  and  dex- 
trine, and  by  the  action  of  strong  sulphuric  acid  is  dissolved 
and  converted  into  that  substance.  This  experiment  is  easily 
made  with  unsized  paper  or  cotton  :  to  two  parts  of  this, 
one  part  of  the  acid  is  very  slowly  added,  taking  care  to 
prevent  an  elevation  of  temperature,  which  would  char  the 
mixture.  In  a  few  hours  the  whole  is  converted  into  a  soft 
mass,  which  is  soluble  in  water,  and  is  principally  dextrine. 
If  the  mixture  is  now  diluted  with  water  and  boiled  for  throe 
or  four  hours,  the  dextrine  is  completely  converted  into 


GUN-COTTON.  411 

grape  sugar,  which  is  obtained  by  neutralizing  the  acid  with 
chalk,  and  evaporation.  By  this  process  paper  or  rags  will 
yield  more  than  their  weight  of  crystallizable  sugar. 

708  The  mutual  convertibility  of  these  different  sub- 
stances is  interesting  in  relation  to  many  of  the  phenomena 
of  vegetable  life.  The  starch  in  the  germinating  seed  is 
changed  by  the  action  of  diastase  into  sugar,  in  which  so- 
luble form  it  seems  better  fitted  for  the  nourishment  of  the 
embryo  plant.  In  the  growth  of  this,  we  have  an  example 
of  the  formation  of  cellulose  from  sugar,  in  which  this 
substance  assumes  a  structural  form  under  the  action  of  the 
vital  force.  This  is  a  transformation  from  the  unorganized 
to  the  organized,  which  mere  chemical  affinity  can  never 
effect. 

709.  Many  unripe  fruits,  as  the  apple,  contain  a  large 
quantity  of  starch,  but  no  sugar.     After  the  fruit  is  fully 
grown,  the  starch  gradually  disappears,  and  in  its  place  we 
find  grape  sugar.     This  change  constitutes  the  ripening  of 
fruits,  and,  as  is  well  known,  will  take  place   after   they 
are  gathered.     In  this  process  we  have  clearly  a  conversion 
of  the   starch  into  sugar,  by  the  agency  of  the  vegetable 
acids  present  in  the  fruit — a  change  which  is  the  reverse  of 
the  previous  one,  and  is  probably  independent  of  life. 

710.  Xyloidine,  Pyroxyline. — The  action  of  strong  nitric 
acid  upon  starch  yields  a  compound  very  similar  to  nitro- 
mannite,  which  is  insoluble  in  water  and  very  combustible  : 
if  we  represent  N04  by  X,  the  formula  of  this  body,  to 
which   the   name   of   xyloidine   has   been   given,   will   be 
C34H1SX2020  =  C3.tH18N2038.     With   sugar  a   similar   sub- 
stance may  be  formed. 

The  action  of  strong  nitric  acid,  or  a  mixture  of  nitric 
and  sulphuric  acids,  upon  woody  fibre,  such  as  paper,  cotton, 
or  sawdust,  gives  rise  to  an  interesting  substance,  which  has 
been  named  pyroxyline,  or  gun-cotton,  as  that  form  of  cellu- 
lose yields  the  purest  product.  The  following  is  an  outline 
of  the  process: — one  hundred  grains  of  clean  cotton  are  im- 
mersed for  five  minutes  in  a  mixture  of  an  ounce  and  a  half 
of  nitric  acid  of  specific  gravity  145  to  1-5,  with  the  same 
measure  of  strong  sulphuric  acid;  it  is  then  removed,  care- 
fully washed  in  cold  water  from  every  trace  of  acid,  and 
dried  at  a  temperature  which  should  not  exceed  120°.  As 
thus  prepared,  it  preserves  the  form  of  the  cotton  unaltered, 
but  has  Iftss  strength  than  the  original  fibre.  Jt  inflames 


412  ORGANIC   CHEMISTRY. 

by  a  very  gentle  heat :  sometimes,  under  circumstances  not 
well  understood,  it  has  been  observed  to  take  fire  at  212°  F. 
Its  combustion  is  instantaneous,  accompanied  by  an  immense 
volume  of  fiame,  and  it  leaves  not  the  slightest  residue. 
When  ignited  in  a  confined  space  it  explodes  with  great 
violence :  one-tenth  of  a  grain  is  sufficient  to  shatter  the 
strongest  glass  tube.  Its  power  in  propelling  balls  is  about 
eight  times  greater  than  that  of  gunpowder;  its  tremendous 
energy  depends  upon  the  fact  that  it  is  completely  resolved, 
by  its  combustion,  into  aqueous  vapor  and  permanent  gases, 
which  are  carbonic  oxyd,  carbonic  acid,  and  nitrogen.  As 
these  arc  much  less  noxious  than  the  gases  resulting  from 
the  combustion  of  gunpowder,  the  gun-cotton  will  be  found 
of  great  use  in  mining.  Its  composition  is  analogous  to 
that  of  nitro-mannite.  There  appear  to  be  two  species,  one 
of  which  is  soluble  in  a  mixture  of  alcohol  and  ether,  and 
the  other  insoluble ;  both  are  generally  present  in  gun- 
cotton.  They  are  substitution  products  from  cellulose,  and, 
representing  N04  by  X,  the  insoluble  form  is  C^HjgX^Ogo, 
and  the  soluble  C^H^X^  =  CMII14N80«.  It  will  be 
seen  that  they  are  formed  from  the  action  of  nitric  acid  with 
the  elimination  of  H30,,  for  each  equivalent  of  the  acid. 
Thus,  C^H20020-h 6NH08  =  Ca4HMNi044+6H.Or 

The  ethereal  solution  dries  rapidly  and  leaves  a  tenacious 
transparent  film  of  pyroxyline  :  it  is  used  in  surgery  for 
covering  wounds  and  abraded  surfaces  from  the  air,  and  is 
known  by  the  name  of  collodion. 

Transformation  of  Woody  Fibre. 

711.  By  the  action  of  atmospheric  air  and  moisture,  wood 
undergoes  a  slow  decay,  dependent  on  the  absorption  of  oxy- 
gen, to  which  Liebig  has  applied  the  term  eremacausis.* 
The  carbon  is  converted  into  carbonic  acid,  while  the  oxygen 
and  hydrogen  of  the  lignine  unite  to  form  water.  The  re- 
sidue is  still  found  to  contain  oxygen  and  hydrogen  in  the 
original  proportions,  but  the  relative  amount  of  carbon  is 
continually  increasing.  For  each  equivalent  of  carbonic 
acid  two  of  water  are  evolved.  The  final  result  of  this  pro- 
cess is  a  brown  or  black  residue,  which  constitutes  vegetable 


*  From  erema,  slow,  and  kausis,  combustion,  a  term  by  which  that 
chemist  denotes  those  changes  which  take  place  in  organic  bodies  from 
the  gradual  action  of  oxygen. 


DESTRUCTIVE   DISTILLATION   OP   WOOD.  413 

mould.  Different  products  of  this  decomposition  have  been 
described  under  the  names  of  humus,  yeine,  ulmine,  humic 
and  ulmic  acids. 

Nearly  all  of  these  bodies  contain  ammonia,  for  which 
they  have  a  strong  affinity :  this  is  in  part  absorbed  from 
the  air,  but  the  experiments  of  Mulder  seem  to  show  that 
they  have  the  power  of  forming  ammonia  from  the  nitrogen 
of  the  atmosphere.  Pure  humic  acid  moistened  and  placed 
in  a  close  vessel  filled  with  air,  is  found  after  some  months 
to  contain  a  considerable  quantity  of  ammonia.  The  hydro- 
gen, evolved  by  a  slow  decomposition  of  the  water,  is  brought 
into  contact  with  nitrogen  under  such  conditions  that  they 
combine  and  produce  the  alkali. 

712.  The  decomposition  of  wood,  when  buried  in  the 
ground  and  excluded  from  the  action  of  the  air,  is  very  dif- 
ferent.    The  oxygen  which  it  contains  gradually  combines 
with  the  carbon  to  form  carbonic  acid,  and  substances  are 
obtained  in  which  the  proportion  of  carbon  and  hydrogen 
is  greater  than  in  the  original  fibre.    Peat,  lignite,  and  bitu- 
minous coal  are  products  of  this  decomposition.     The  car- 
bon and  hydrogen  in  coal   combine  in  various  ways,  and 
often  generate  vast  quantities  of  gaseous  carburets  of  hydro- 
gen, (450.)    Anthracite  has  resulted  from  the  action  of  heat 
on  bituminous  coal,  which  has  expelled  all  the  volatile  in- 
gredients, and  left  a  residue  of  nearly  pure  carbon. 

Destructive  Distillation  of  Wood. 

713.  The  principal  products  of  the  decomposition  of  wood 
by  heat  are  carbonic  acid  gas,  water,  and  gaseous  carburets 
of  hydrogen.    With  the  water  are  mixed  several  other  bodies, 
among  which  are  acetic  acid  and  pyroxylic  spirit,  presently 
to  be  described,  and  a  quantity  of  oily,  tar-like  substance, 
containing  several  interesting  bodies,  which  we  shall  mention. 
These  products  are  .obtained  on  a  large  scale  by  distilling 
wood  in  iron  cylinders ;   the  quantity  of  acetic  acid  is  so 
considerable  that  the  process  has  become  important  in  the 
arts. 

Kreasote. — This  substance  occurs  dissolved  in  the  crude 
acetic  acid  from  wood,  and  is  separated  and  purified  by 
a  complicated  process.  It  is  a  colorless  oily  fluid,  which 
boils  at  397°,  and  has  a  specific  gravity  of  1-037.  It  1ms  a 
peculiar  and  very  persistent  odor,  resembling  that  of  smoke, 
and  a  powerful  burning  taste.  It  is  soluble  in  about  100 


414  ORGANIC   CHEMISTRY. 

parts  of  water,  and  the  solution  possesses  powerful  antiseptic 
qualities.  Meat  which  has  been  soaked  in  it  is  incapable 
of  putrefaction,*  and  acquires  a  delicate  flavoi  of  smoke. 
The  power  of  wood-smoke  to  preserve  flesh  is  due  to  the 
presence  of  kreasote.  It  is  a  corrosive  poison  when  taken 
in  any  quantity,  but  a  dilute  solution  is  used  medicinally, 
both  internally  and  externally,  as  a  styptic  and  antiseptic. 
The  composition  of  kreasote  is  C14H803.  It  combines  with 
the  alkalies  to  form  crystalline  compounds. 

714.  Wood-tar  contains  several  carburets  of  hydrogen,  one 
of  which,  called  eupion,  is  an  oily,  fragrant  liquid,  of  the 
specific  gravity  -655,  being  the  lightest  liquid  known.     Its 
formula  is,  probably,  C6H6. 

Paraffin. — This  is  a  white  crystalline  substance,  obtained 
from  the  less  volatile  portions  of  wood-tar.  It  crystallizes 
in  delicate  needles,  which  fuse  at  110° ;  it  is  soluble  in  alco- 
hol and  ether.  Its  formula  is  C43II50.  Paraffin  is  obtained 
in  large  quantities  by  the  dry  distillation  of  beeswax. 

715.  Coal-tar  consists  principally  of  a  mixture  of  various 
hydrocarbons;  some  of  these  are  liquid  and  very  volatile, 
constituting  what  is  called  gas  naphtha.     Among  the  less 
volatile  products  are  two  solid  carburets  of  hydrogen,  naph- 
thalen,  and  paranaphtJialen,  or  anthracen.    The  first  of  these 
is  formed  by  the  decomposition  of  many  organic  matters 
by  heat.      Its  formula  is  C20H8 :   it  is  volatile,  and  forms 
beautiful  pearly  crystals  of  a  fragrant  odor.     The  action  of 
chlorine,  bromine,  and  nitric  acid  on  naphthalen,  gives  rise 
to  a  great  number  of  compounds.     They  are  formed  by  suc- 
cessive substitutions  of  the  hydrogen  by  one  or  more  of  these 
substances,  and  many  metameric  modifications  of  these  bodies 
exist.     Thus,  the  bichlorinized  naphthalen  C20H6C13  occurs 
in  seven  modifications,  which  are  perfectly  distinct  in  their 
characters.     We  are  led  to  suppose  that  these  compounds 
owe  their  different  properties  to  a  different  arrangement  of 
their  constituent  atoms,  and  it  is  easy  to  see  that,  in  this 
way,  the  number  of  possible  combinations  will  be  immense. 
More  than  twenty  substances  have  been  described,  in  which 
chlorine  is  in  part  substituted  for  the  hydrogen  of  the  naph- 
thalen.    The  final  product  of  the  action  of  chlorine  is  C20C18, 
being  a  chlorid  of  carbon,  which  preserves  the  type  of  naph- 
thalen.    In  addition  to  these,  coal-tar  contains  a  consider- 

*  Hence  the  name,  from  the  Greek  kreas,  flesh,  and  soto,  I  preserve. 


ALCOHOLS.  415 

able  proportion  of  a  body  named  phenol,  and  several  organic 
alkaloids.  The  watery  products  of  the  distillation  of  coal 
hold  a  large  quantity  of  ammonia  in  solution,  often  combined 
with  hydrosulphuric  and  hydrocyanic  acids. 

716.  Petroleum. — In  many  parts  of  the  world  an  oily 
matter  exudes  from  the  rocks,  or  floats  on  the  surface  of 
springs.  The  principal  sources  of  this  substance  are  Amiano 
in  Italy,  Ava,  and  Persia,  but  it  is  found  in  many  places  in 
our  own  country.  The  well-known  Seneca  oil  is  an  instance 
of  this  kind.  Petroleum  is  a  variable  mixture  of  several 
bodies.  By  distillation,  it  yields  a  colorless  liquid,  called 
naphtha,  which  is  very  light,  volatile,  and  combustible.  Its 
formula  is,  probably,  C13H10.  Naphtha  occurs  nearly  pure 
in  Italy  and  Persia,  and  is  used  for  illumination. 

Petroleum  contains  a  variety  of  other  bodies,  among  which 
are  paraffin,  and  several  resinous  matters,  formed,  perhaps, 
by  the  oxydation  of  naphtha.  These  substances  are  pro- 
bably derived  from  coal  or  other  matters  of  vegetable  origin. 

ALCOHOLS. 

717.  This  series  of  compounds  has  already  been  alluded  to 
in  explaining  the  principle  of  homology.  The  alcohols  may 
be  represented  by  CnHw4_303,  n  being  a  number  divisible 
by  two :  all  of  them  by  oxydizing  agents  lose  H3  and 
combine  with  03  to  form  monobasic  acids,  whose  general 
formula  is  C^Hn04.  Of  these  acids  we  have  now  nearly  a 
complete  series  up  to  the  stearic  acid,  in  which  n  =  38. 
But  a  few  of  the  corresponding  alcohols  are  known  j  the 
principal  are  methol  C3H403,  wine  alcohol  C4HG03,  amylic 
alcohol  oramylol  C10H1303,  and  cctic  alcohol  or  cetol  C33H3403. 
We  shall  first  describe  the  alcohol  of  wine,  to  which  we 
may  conveniently  give  the  name  of  vinol :  it  is  the  best 
known  and  most  important  of  the  series,  and  will  serve  to 
illustrate  the  history  of  the  others. 

VINOL — COMMON  ALCOHOL,  C4H603. 

This  substance  has  long  been  known  under  the  name 
of  alcohol,  or  spirits  of  wine.  We  have  already  explained 
the  manner  in  which  it  is  obtained  as  a  result  of  the  fer- 
mentation of  sugar.  The  vinous  fermentation  in  the  juice  of 
the  grape  and -other  fruits,  in  an  infusion  of  malt,  or  in  the 


416 


ORGANIC   CHEMISTRY. 


syrup  of  the  sugar-cane,  always  results  in  the  conversion  of 
the  sugar  which  it  contains,  into  alcohol  and  carbonic  acid 
gas.  When  the  fermentation  is  arrested  before  all  of  the 
Bugar  is  decomposed,  tho  wine  is  sweet;  if  the  liquor  is 
bottled  before  the  action  is  finished,  the  excess  of  carbonic 
acid  remains  in  solution,  and  gives  an  effervescent  and  spark- 
ling property,  as  in  bottled  beer  and  champagne. 

When  these  fermented  liquors  are  distilled,  the  alcohol, 
boiling  at  a  lower  temperature  than  water,  passes  over 
first.  By  repeated  distillation  in  this  way,  a  liquid  is 
obtained  which  contains  85  parts  of  alcohol  in  100.  To 
obtain  it  free  from  water,  it  is  digested  with  quicklime,  or 
better  with  fused  chlorid  of  calcium,  which  combines  with 
the  water.  The  mixture  is  then  distilled  in  a  water-bath, 
and  pure  alcohol  passes  over.  A  convenient  apparatus  for 
condensing  the  vapor  of  alcohol,  ethers,  and  other  volatile 
substances,  is  shown  in  figure  412. 


Fig.  412. 

The  retort  r  is  connected  with  a  glass  condensing  tube  t, 
about  which  a  metallic  tube  ra  is  secured  by  corks  at  the  ends, 
leaving  a  water-tight  space  between  the  two.  A  funnel  tube 
/  conducts  cold  water  from  the  tank  w  to  the  lower  end  of 
the  condenser.  This  escapes  at  the  upper  orifice  o,  thus 
maintaining  a  constant  current  of  cold  water,  by  means  of 
which  the  vapors  of  even  very  volatile  liquids  are  easily 
condensed. 

718.  Pure  or  absolute  alcohol  is  a  colorless  fluid,  with  a 
specific  gravity  of  about  -800,  and  boils  at  173°  F.  Its  den- 


ACTION    OF   ACIDS   UPON   ALCOHOL.  417 

sity  varies  very  much  with  its  temperature,  (102  ;)  thus  at 
82°  it  is  0-815  ;  at  50°,  -8065  ;  at  59°,  -8021  ;  at  68°,  -7978  ; 
and  at  77°,  -7933.  It  has  a  pungent  and  agreeable  taste 
and  a  fragrant  odor.  It  is  very  combustible,  and  burns 
with  a  pale  blue  flame  without  smoke,  which  renders  it  very 
useful  as  a  source  of  heat  in  chemical  processes.  The  action 
of  alcohol  on  the  system  is  well  known  as  that  of  a  power- 
ful and  dangerous  stimulant.  It  is  largely  used  in  the 
operations  of  the  arts,  the  preparation  of  medicines,  and  the 
processes  of  chemistry.  Its  solvent  powers  are  very  great  : 
the  volatile  oils  and  resins  are  dissolved  by  it,  as  well  as 
many  acids  and  salts,  the  caustic  alkalies,  and  a  large  num- 
ber of  other  substances. 

The  density  of  alcohol  vapor  is  1589-4,  and  its  equivalent 
is  represented  by  four  volumes,  oxygen  being  one  volume  ; 
thus  — 

4  volumes  of  carbon  vapor  .............     4X     829.       =     3316'0 

12         "       «  hydrogen  ..................  12  X       69-2     =       830-4 

2        «       «  oxygen  ....................     2  X  1105-6     =     2211-2 

635776 
Equal  4  volumes  alcohol  vapor,  of  which  1  volume  weighs....  1598-4 

719.  Pure  alcohol  dissolves  several  salts,  as  the  chlorid 
of  calcium  and  the  nitrates  of  lime  and  magnesia,  and  forms 
with  them  crystalline  compounds,  in  which  the  alcohol  takes 
the  place  of  the  water  of  crystallization,  by  virtue  of  the 
homologous  relation  which  it  sustains  to  water.  When  potas- 
sium is  added  to  alcohol  free  from  water,  hydrogen  is  evolved 
and  a  crystalline  compound  formed,  in  which  the  metal 
replaces  hydrogen.  It  is  C4H.K02,  and  by  the  action 
of  water  is  decomposed  into  alcohol  and  hydrate  of  potash, 
C4ELK03-f  H302=  C4H6O2-f  (KH)03.  By  an  indirect  pro- 
cess, a  compound  is  obtained  in  which  the  oxygen  of  alcohol 
is  replaced  by  sulphur,  and  which  is  C4H6S2.  It  is  a  colorless 
very  volatile  liquid,  having  a  strong  odor  resembling  that  of 
onions.  Like  the  oxygen  species,  it  may  exchange  H  for  a 
metal  ;  with  oxyd  of  mercury  it  forms  water  and  a  crystal- 
line compound  C^H5HgSa  :  from  the  violence  of  the  action 
it  has  received  the  fanciful  name  of  mercaptan,  (from  mer- 


Action  of  Acids  upon  Akohol. 

720.  It  has  been  shown   that  when  n  in  the   general 
formula  of  the  alcohols  becomes  equal  to  zero}  we  have 

27 


418  ORGANIC   CHEMISTRY. 

water  H302,  which  may  be  regarded  as  their  homologuc  and 
prototype.  We  have  farther  pointed  out  the  fact  that  a 
group  of  elements  is  often  found  to  be  equivalent  to  an  atom 
of  hydrogen,  and  capable  of  replacing  it  in  combination : 
such  is  NH4in  the  ammonia  salts;  and  in  the  compounds  of 
vinic  alcohol,  the  group  C4H5  will  be  found  to  sustain  simi- 
lar relations.  In  water,  which  is  (HH)Oa,  one  atom  of 
hydrogen  may  be  replaced  by  this  group,  and  we  have  then 
(C4H5.H)Oa,  which  is  alcohol.  In  the  potassium  compound 
just  described,  the  second  atom  of  hydrogen  is  replaced  by 
a  metal,  and  we  shall  presently  describe  a  compound  in 
which  both  atoms  of  the  hydrogen  are  replaced  by  the 
organic  group:  it  is  (C4H5.C4H5)03==C8H1003.  This 
same  group  may  also  replace  the  hydrogen  in  acids;  a 
monobasic  acid  reacts  with  one  equivalent  of  alcohol  and 
eliminates  an  equivalent  of  water,  forming  a  compound  in 
which  C4H5  replaces  H  in  the  acid,  and  renders  it  neutral. 
Such  compounds  are  called  ethers  of  the  various  acids. 
With  bibasic  and  tribasic  acids,  two  and  three  equivalents 
of  alcohol  combine  to  form  neutral  ethers,  and  eliminate  two 
and  three  equivalents  of  water.  But  when  a  bibasic  acid  re- 
acts with  but  one  equivalent  of  alcohol,  only  one  atom  of  its 
hydrogen  is  replaced,  and  the  second  atom  remains  as  be- 
fore, capable  of  being  exchanged  for  a  metal.  Such  com- 
pounds are  acid  ethers  or  vinic  acids. 

721.  Although  the  ethers  are  thus  analogous  to  salts  in 
their  constitution,  they  are  less  readily  decomposed  than  the 
corresponding  metallic  salts ;  they  frequently  require  the  aid 
of  heat  to  effect  the  breaking  up  of  the  combination,  and  are 
generally  more  stable  as  their  equivalent  is  more  elevated. 

The  neutral  ether  containing  sulphuric  acid,  for  example, 
does  not  precipitate  salts  of  baryta,  and  the  corresponding 
vinic  acid  forms  a  soluble  s&t  with  that  base.  In  these, 
and  many  other  instances,  the  properties  of  the  acids  seem 
masked  in  their  ethers,  but  similar  cases  are  met  with  in 
the  salts  of  inorganic  bodies. 

722.  The  action  of  chlorohydric  acid,   and  other  acids 
containing  no  oxygen,  upon  alcohol,  requires  a  little  explana- 
tion.    We  have  seen  that  when  HC1  acts  upon  a  metal,  the 
compound  eliminated  is  of  the  type  Ha ;  but  when  the  hy- 
dracid  acts  upon  a  hydrated  oxyd,  as  (KII)03,  the  same 
chlorid  is  formed,  and  H302  is  evolved;  so  it  is  with  al- 
cohol, which  with  hydrochloric  acid  yields  water  and  a  body 


ETHERS.  419 

C4HS01.  As  C4H5  is  equivalent  to  H,  the  new  ether  repre- 
sents chlorohydric  acid,  and  is  evidently  the  chlorinized 
species  of  a  hydrocarbon  C4H6,  which  should  yield  with 
(Cla)  the  same  product,  as  a  result  of  direct  substitution.  As 
water  H30a  is  the  prototype  of  the  alcohols,  so  (Ha)  is  the 
prototype  and  homologue  of  the  carbohydrogens  like  C4H8, 
whose  formula  is  C  J!n+2  — CMHn-fH3;  and  chlorohydrio 
acid  HC1  is  the  type  of  the  chlorohydric  ethers. 

As  the  ethers  of  alcohol  contain  04H5,  replacing  H  in 
the  acids,  and  consequently  differ  from  the  latter  by  (C2H2)3, 
it  follows  that  the  ethers  are  always  homologous  with  their 
parent  acids. 

In  describing  these  compounds,  we  shall  often  designate 
the  group  C4H5  by  the  symbol  Et,  and  write  alcohol  (EtH)Oa. 

Ethers. 

723.  Chlorohydric  Ether,  CJI£l==fttCl.— When  alcohol 
is  saturated  with  chlorohydric  acid  gas,  and  heated,  it  is  con- 
verted into  water  and  this  ether,  (EtH)03+HCl  =  EtCl  -f- 
H20a.  By  distillation  it  is  obtained  as  a  pungent  aromatic 
liquid,  slightly  soluble  in  water,  and  boiling  at  52°  F. :  at 
a  temperature  of  — 4°  it  crystallizes  in  cubes:  its  specific 
gravity  is  '873. 

By  distilling  alcohol  with  hydrobromic  acid,  or  a  mixture 
of  phosphorus  and  bromine,  which  evolves  the  acid,  hydro- 
bromic  ether  EtBr,  is  obtained  as  a  volatile  liquid  heavier 
than  water;  and  by  substituting  iodine  for  bromine,  liydriodic 
ether  EtI  is  found.  It  is  a  colorless  liquid,  with  a  specific 
gravity  of  1-920,  and  a  boiling  point  of  160°  F.  These 
ethers  are  all  decomposed  by  an  alcoholic  solution  of  hydrate 
of  potash  into  alcohol  and  a  potassium  salt,  EtCl-f-(KH)0,1, 
=  (EtH)02-|-KCl.  By  the  action  of  potassium  upon  chlo- 
rohydric ether,  a  compound  is  obtained  in  which  K  replaces 
Cl.  It  is  C4H5K  orEtK  :  this  is  decomposed  by  water  into 
hydrate  of  potash  and  a  volatile  oily  substance  C4II6,  to 
which  the  name  of  acetene  has  been  given.  It  is  the  hydro- 
carbon corresponding  to  Ha,  and  may  be  written  EtII. 
Another  product  has  been  formed,  which  is  C8H10,  in  which 
the  second  atom  of  hydrogen  is  replaced  by  C4H. :  it  is  EtEt, 
and  has  a  density  corresponding  to  four  volumes  of  vapor. 
The  binary  grouping  which  prevails  throughout  all  com- 
pounds is  such  as  to  forbid  the  isolation  of  the  elements 
C4H5,  which  are  always  grouped  with  a  metal,  chlorine,  or 


420  ORGANIC    CHEMISTRY. 

even  another  equivalent  of  themselves,  so  that  the  law  of 
divisibility  is  never  violated. 

724.  Nitric  Ether  N(Et)0B  =  N(C4H5)06.— The  action  of 
alcohol  and  nitric  acid  is  violent  and  irregular,  the  alcohol 
being  oxydized  at  the  expense  of  the  oxygen  of  the  acid,  and 
several  compounds  formed ;  but  the  addition  of  a  little  urea 
or  nitrate  of  ammonia  to  the  mixture  of  the  acid  and  alcohol 
prevents  this,  and  the  ether  is  then  formed  and  distilled  over 
by  the  aid  of  heat ;  water  being  the  only  other  product.  Nitric 
acid  N05HO  =  NH06+(EtH)Oa=NEt06H-HaOa.    It  is  a 
colorless  liquid  of  a  sweet  taste,  is  heavier  than  water,  in  which 
it  is  insoluble,  and  boils  at  185°  F.  Its  vapor  explodes  by  heat. 

725.  Nitrous  Ether,   or  Hyponitric  Ether,  N(Et)04  = 
C4H5N04. — When  nitric  acid  acts  upon  starch,  copious  red 
vapors  are  evolved,  which  are  anhydrous  hyponitric  acid  N03 : 
they  are  rapidly  absorbed  by  dilute  alcohol,  with  the  produc- 
tion of  sufficient  heat  to  cause  the  new  ether  to  distil  over,  when 
it  is  condensed  by  means  of  ice.     Hyponitric  acid  N03HO  = 
NH04+(EtH)03=N(Et)04+H8Oa.    The  hyponitric  ether 
is  a  pale  yellow  liquid,  having  a  fragrant  odor  of  apples :  it  boils 
at  62°,  and  has  a  specific  gravity  of  -947.   It  is  one  of  the  pro- 
ducts of  the  action  of  nitric  acid  with  alcohol,  when  urea  is 
not  added;  and  a  solution  of  the  impure  product  in  alcohol, 
obtained  by  distilling  alcohol  with  nitre  and  sulphuric  acid, 
constitutes  the  sweet  spirits  of  nitre  of  the  old  chemists,  which 
is  still  used  in  medicine.    If  a  mixture  of  nitric  acid  and  alco- 
hol is  distilled  with  the  addition  of  turnings  of  metallic  cop- 
per, pure  nitrous  ether  may  be  obtained.      Nitrous  ether 
undergoes  a  remarkable   decomposition  by  the  action   of 
sulphuretted  hydrogen :  the  gas  is  rapidly  absorbed,  with  the 
separation  of  sulphur,  and  alcohol,  water,  and  ammonia  are 
formed ;  C4H6N04+3H  .Sfl  =  S6+H203-|-C4H60+NH3. 

Perchloric  ether  is  obtained  by  an  indirect  process  as  an 
oily  liquid,  heavier  than  water,  having  a  sweet,  pungent  taste, 
like  oil  of  cinnamon.  It  explodes  by  slight  friction,  heat, 
or  percussion,  with  fearful  violence.  Perchloric  acid  being 
C107HO  =  C1H08,  the  ether  is  C1(C4IL)08.  Like  the  nitric 
and  hyponitric  ethers,  it  is  decomposed  by  an  alcoholic  solu- 
tion of  hydrate  of  potash  into  alcohol  and  a  perchlorate. 

Sulphovinic  Acid.   . 

726.  When    sulphuric    acid,  mixed  with  its  weight  of 
alcohol,  is  heated  to  boiling,  combination  ensues  with  the 


SULPHOVINIC   ACID.  421 

elimination  of  water,  and  sulphovinic  acid  is  formed;  sul- 
phuric acid  S?H308+(EtH)Oa=S2(EtH)08+Ha03.  By 
diluting  the  mixture  with  water  and  saturating  it  with  car- 
bonate of  lime,  the  free  sulphuric  acid  is  converted  into 
insoluble  sulphate  of  lime,  and  the  soluble  sulphovinate  is 
obtained  by  evaporating  at  a  gentle  heat  and  cooling,  in 
colorless  prisms.  As  the  carbohydrogen  elements  have  re- 
placed one  equivalent  of  hydrogen  in  the  sulphuric  acid,  the 
new  acid  is  monobasic,  and  the  lime  salt  is  S3(EtCa)Oa 
-f-HflOa :  this  water  of  crystallization  is  lost  in  a  dry  atmo- 
sphere. By  substituting  carbonate  of  baryta  for  lime,  the 
baryta  salt  S3(EtBa)08  is  obtained  in  fine  crystals;  from 
this  salt,  by  double  decomposition,  the  sulphovinates  of 
other  bases  may  be  obtained.  Dilute  sulphuric  acid  preci- 
pitates all  the  baryta  from  the  baryta  salt,  and  sulpho- 
vinic acid,  S2(EtH)08  is  obtained  in  solution  :  when  concen- 
trated in  vacuo  it  forms  a  syrupy  liquid,  which  is  decomposed 
by  heat  into  alcohol  and  sulphuric  acid,  by  taking  up  the 
elements  of  water.  The  lime  and  baryta  salts  undergo,  in 
part,  a  similar  decomposition  by  boiling,  and  after  several 
years,  even  at  the  ordinary  temperature,  are  changed  into 
sulphates  and  alcohol. 

With  hydrate  of  potash  a  similar  change  takes  place  by 
heat,  and  alcohol  and  a  sulphate  are  formed.  Sulphovinate 
of  potash  S3(KEt)08-f(KH)03=S2K308-h(EtH)03;  or 
neutral  sulphate  of  potash  and  alcohol.  If  the  hydro-sul- 
phuret  of  potash  KS.HS  =  (KH)Sfl  is  employed,  sulphur- 
alcohol  (EtH)S3  is  formed  by  a  similar  reaction ;  and  with  any 
salt,  like  the  acetate  of  potash  C4H3K04,  a  compound  is  ob- 
tained, in  which  Et  replaces  K  :  it  is  C4H3(Et)04,  or  acetic 
ether.  In  this  way  the  perchloric  and  many  other  ethers 
are  formed  by  double  decomposition. 

727.  When  carefuHy  dried  sulphovinate  of  potash  is  dis- 
tilled with  a  mixture  of  potassic  alcohol  (EtK)02,  sulphate 
of  potash  is  formed,  and  a  volatile  liquid  distils  over,  in 
which  the  second  atom  of  H  is  replaced  by  the  elements 
C4H5.  S3(EtK)08-f-(EtK)03r=S3K308+(EtEt)03.  This 
compound  is  also  obtained  when,  within  certain  limits  of  tem- 
perature, sulphovinic  acid  acts  upon  alcohol;  SB(EtH)O8 
-|-(EtH)03==S3H308-f  (EtEt)03  being  the  products.  The 
result  of  this  complete  substitution  may  be  conveniently 
designated  as  hydrovinic  ether,  precisely  as  alcohol  is  hydro- 
vinic  acid.  It  has  long  been  known  in  the  history  of  tho 


422  ORGANIC   CHEMISTRY. 

science  under  the  simple  name  of  ether,  which  has  since  beec 
extended  to  a  great  number  of  allied  products,  and  has 
become  a  generic  term.  It  is  a  colorless,  limpid,  volatile 
liquid,  and  as  its  vapor  is  very  combustible,  should  never 
be  brought  near  a  flame.  It  has  a  specific  gravity  of  -725, 
and  boils  under  the  ordinary  pressure  of  the  atmosphere  at 
96°  F. :  by  its  rapid  spontaneous  evaporation  it  produces 
great  cold.  It  is  sparingly  soluble  in  water,  and  the  ether 
of  the  shops,  which  often  contains  alcohol,  may  be  purified 
by  agitation  with  its  volume  of  water,  which  dissolves  the 
alcohol,  while  the  ether  floats  upon  the  surface.  Although 
in  the  liquid  state  it  is  lighter  than  alcohol,  its  vapor  is 
much  heavier.  The  density  of  ether  vapor  is  2556-3 ;  four 
volumes  then  equal  10227*2,  and  contain  two  equivalents,  or 
eight  volumes  of  alcohol,  minus  one  equivalent,  or  four  vo- 
lumes of  water : 

2  equivalents  of  alcohol  vapor,  2  X  6357*6 =  12715-2 

1  equivalent  of  water  HaOa —     2488-0 

1  equivalent,  or  four  volumes  of  ether  vapor =  10227*2 

1  volume  of  ether  vapor 2556-3 

Its  equivalent  is  therefore  2C4H003  =  C8H1304 — H303= 
C8H1002,  or  Eta03. 

728.  Ether  is  used  in  the  arts  and  in  many  chemical  pro- 
cesses as  a  solvent;  and  in  medicine,  internally  as  a  stimu- 
lant, and  externally  as  a  refrigerant,  from  the  cold  produced 
by  its  evaporation.    An  important  application  was  some  years 
since  pointed  out  by  Dr.  Charles  T.  Jackson,  of  Boston,  and 
introduced  into  practice  by  Mr.  Morton,  a  dentist  of  that 
city  :  it  depends  upon  the  fact  that  the  vapor  of  ether,  when 
mixed  with  atmospheric  air  and  inhaled,  produces  a  kind  of 
intoxication,  followed  by  a  state  of  stupor,  in  which  it  was 
found  by  these  gentlemen  that  the  subject  is  so  far  insensi- 
ble to  external  impressions,  as  to  undergo  the  most  difficult 
surgical  operations  without  pain.     This  important  discovery 
has  been  very  extensively  applied  both  in  this  country  and 
in  Europe  ;*  and  the  vapor  of  several  other  liquids  has  been 
found  to  produce  similar  effects. 

729.  In  the  manufacture  of  ether  on  a  large  scale,  the 
reaction  of  sulphovinic  acid  and  alcohol  is  employed.    When 

*  The  French  government,  in  token  of  the  high  importance  of  the  dis- 
covery, has  bestowed  upon  Dr.  Jackson  the  Cross  of  the  Legion  of  Honor. 


ETHERS.  423 

the  mixture  of  alcohol  and  sulphuric,  acid  containing  sul- 
phovinic  acid  and  water,  is  diluted,  so  as  to  boil  much 
below  300°  F.,  it  is,  as  we  have  already  shown,  decomposed 
again  into  sulphuric  acid  and  alcohol ;  but  at  about  300°  F., 
the  sulphovinic  acid  reacts  upon  a  second  equivalent  of 
alcohol  instead  of  an  equivalent  of  water,  and  yields  sul- 
phuric acid  and  ether.  By  an  ingenious  method,  the  alter- 
nate formation  and  decomposition  of  sulphovinic  acid  may 
be  made  to  furnish  an  unlimited  supply  of  the  new  pro- 
duct. The  arrangement  is  represented  in  the  fig.  413. 
A  mixture  of  five  parts  of  alcohol  of  90  per  cent,  and 


Fig.  413. 

eight  parts  of  ordinary  sulphuric  acid  is  placed  in  the 
flask  e,  through  the  cork  of  which  passes  a  thermometer  t, 
and  two  tubes,  one  of  which  d,  conveys  the  vapors  away  to 
a  condenser  B,  while  the  other  a,  which  dips  below  the 
surface  of  the  liquid,  is  arranged  to  supply  pure  alcohol 
from  a  reservoir  E.  The  mixture  is  now  raised  to  its  boil- 
ing point,  which  is  about  300°  F.,  and  carefully  maintained 
at  that  temperature,  so  as  to  be  in  constant  ebullition.  Al- 
cohol is  slowly  admitted  through  the  cock  /,  in  sufficient 
quantity  to  preserve  the  original  level  of  the  liquid  in  the 
flask.  In  this  way,  as  the  sulphovinic  acid  meets  with  tho 


424  ORGANIC   CHEMISTRl 

alcohol,  it  is  decomposed  into  ether  and  sulphuric  acij,  but 
this  reacting  upon  another  portion  of  alcohol,  forms  water, 
which  is  volatilized,  and  a  new  portion  of  sulphovinic  acid, 
to  be  decomposed  in  its  turn.  The  ether  and  water  distil 
over  and  are  condensed  together;  and  the  same  portion  of 
sulphuric  acid  will  serve  to  convert  an  indefinite  quantity 
of  alcohol  into  water  and  ether;  a  trace  only  of  the  sul- 
phuric acid  passes  over.  The  ether  is  decanted  from  the 
water,  and  purified  by  distilling  from,  a  small  quantity  of 
hydrate  of  potash. 

730.  As  it  has  long  been  obtained  by  the  distillation  of 
sulphuric  acid  with  alcohol,  it  was  formerly  called  sulphu- 
ric ether,  a  name  which  is  still  sometimes  retained.    The  true 
sulphuric  ether,  which  corresponds  to  the  other  neutral  ethers, 
is    obtained    by   the   action   of  anhydrous  sulphuric  acid 
upon  hydric  ether.     It  is  a  neutral,  dense,  oily  fluid,  and 
differs  from  sulphovinic  acid  in  having  the  second  equiva- 
lent of  II  replaced  by  Et,  its  formula  being  S2(Et3)08.     By 
heat  it  is  decomposed,  in  the  presence  of  water,  into  sul- 
phovinic acid  and  alcohol. 

731.  Compounds  have  been  obtained  which  correspond 
to  ether  in  which  03  is  replaced  by  sulphur,  selenium,  and 
tellurium.     The  sulphur  compound  is  C8H10S3  or  Et3S3,  and 
is  obtained  by  the  action  of  hydrochloric  ether  upon  sul- 
phuret  of  potassium  2EtCl+KflS8  =  2KCl-j-Et9Ss :  with 
bisulphuret  of  potassium,  a  compound  is  obtained  which  is 
Et3S4,  and  corresponds  to  persulphuret  of  hydrogen  HaS4. 
These  are  volatile  liquids,  insoluble  in  water,  and  having 
a  strong  odor  like  garlic. 

732.  Phosphoric  acid  yields  several  compounds  contain- 
ing the  elements  of  alcohol.     The  tribasic  acid  is  P05.3HO 
=  PII308,  and  the  neutral  phosphoric  ether  is  P(Et3)08. 
The  other  two  compounds  are  P(Et3H)08  and  P(EtH3)08, 
and    are  respectively  monobasic    and  bibasic  vinic  acids. 
Cart  ovinate  of  potash  is  obtained  when  carbonic  acid  gas 
is  passed  into  a  solution  of  hydrate  of  potash  in  pure  alcohol. 
The  acid  being  CflHfl06,  the  new  salt  is  C2(EtK)0B.     The 
acid  has  not  been  isolated.      The  true  carbonic  ether  is 
Ca(Eta)06=C10H1006.     By  substituting  bisulphuret  of  car- 
bon for  carbonic  acid  gas  in  the  above  process,  carbovinatea 
are  obtained  iu  which  the  oxygen  is  in  part  replaced  by 
sulphur.     The  acid  is  obtained  in  a  separate  form,  and  ia 


OIEFJANT   GAS. 


425 


Oa(EtH)(OaS4);  from  the  yellow  color  of  some  of  its  salts, 
it  has  been  called  xantliic  add. 

733.  Silicic  Ethers. — The  action  of  chlorid   of  silicon 
upon  alcohol  yields  two  silicic  ethers.     They  are  odorous, 
pungent,  and  volatile  liquids,  which  are  rapidly  decomposed 
by  alkalies,  like  the  other  ethers,  and  slowly  by  water  alone ; 
when  exposed  to  moist  air,  in  imperfectly  closed  vessels,  they 
evolve  alcohol  and  are  gradually  decomposed,  leaving  hy« 
drated  silicic  acid  in  beautiful  transparent  masses,  resem- 
bling rock  crystal.     The  formula  of  one  is  represented  by 
C13H15Si06   which    corresponds  to   a   tribasic   silicic   acid 
Si03.8HO  =  SiH306,    and   is    Si(Et3)06.     The    other    is 
C8H10Si4014,  which  represents  a  bibasic  acid  4Si034-H3Oa 
=Si4H3014;  the  ether  being  Si4Eta014. 

Chlorid  of  boron  with  alcohol  yields  two  similar  ethers : 
they  burn  with  the  fine  green  flame  characteristic  of  boracic 
acid.  Boracic  ether  is  formed  when  alcohol  is  distilled  from 
boracic  acid,  and  is  the  cause  of  the  green  flame  of  an  alco- 
holic solution  of  the  acid. 

734.  Olefiant  Gas,  C4H4. — When  alcohol  is  mixed  with 
so  much   sulphuric  acid  that  the  mixture  does  not   boil 
below    320°  F.,  the    sulphovinic   acid  which    is   formed, 
undergoes  a  decomposition  different  from  those  already  de- 
scribed ;  it  breaks  up  directly  into  sulphuric  acid  and  ole 
fiant  gas,  S2(C4H5H)08  =  S2(H2)08+C4H4. 

A  more  elegant  way  of  preparing  it  is  by  an  arrange- 
ment similar  to  that  used  for  pro- 
ducing ether.  Sulphuric  acid  is 
diluted  with  nearly  one-half  its 
weight  of  water,  so  that  its  boil- 
ing point  is  between  320°  and 
330°,  and  being  heated  in  the  flask 
a  (fig.  414)  to  ebullition,  the  vapor 
of  boiling  alcohol  is'  introduced 
from  the  flask  d  by  the  tube  6, 
which  dips  a  little  way  in  the  acid. 
In  this  process,  we  may  suppose 
that  sulphovinw  acid  is  formed 
with  the  escape  of  an  equivalent 
of  water  in  vapor,  and  is  then  im- 
mediately decomposed  into  sul- 
phuric acid  and  olefiant  gas;  an 
equivalent  of  alcohol  yields  C4lI4-fIIflOa.  The  gas  is  thus 


Fig.  414. 


426  ORGANIC   CHEMISTRY. 

obtained  quite  pure,  and  the  process  may  be  continued  for 
any  length  of  time.  This  compound  is  a  product  of  the 
destructive  distillation  of  many  organic  substances,  and  is 
abundant  in  the  gases  for  illumination  prepared  by  the 
decomposition  of  coal  and  the  fat  oils. 

735.  When  mingled  with  its  own   volume  of  chlorine 
combination  ensues,  and  the  product  condenses  as  a  heavy  oily 
liquid  of  a  sweet  pungent  taste.     It  was  discovered  by  an 
association   of   Dutch   chemists,  who,  from   this  reaction, 
gave  to  the  carbohydrogen  the  name  of  olefiant  gas.     It  is 
C4H4C13,  and  corresponds  to  a  carbohydrogen  C4H6,  identical 
in  composition  with  aceten.  By  the  action  of  chlorine  a  series 
of  compounds  is  formed  by  successive  substitutions ;  we  have 
C4H3C1?,  C4H2C14,  C2HC15  and  C4C18;  A  similar  series  of  com- 
pounds is  obtained  from  chlorohydric  ether,  which,  though  re- 
presented by  the  same  formulas,  are  unlike  in  their  properties : 
the  two  series  afford  an  interesting  case  of  metamerism. 

The  final  product  of  the  action  of  chlorine  upon  both 
series  of  compounds  is  the  chlorid  of  carbon  C4C16.  This 
is  a  white  crystalline  solid,  with  an  aromatic  odor,  like  cam- 
phor; it  melts  at  320°,  and,  at  a  temperature  a  little  above 
this,  may  be  distilled  unaltered.  It  is  scarcely  combustible, 
and  is  unchanged  by  acids  or  alkalies.  When  its  vapor  is  pas- 
sed through  a  porcelain  tube  heated  to  redness,  it  is  resolved 
into  chlorine  gas  and  a  new  compound  C4C14,  which  is 
a  volatile  liquid,  of  the  specific  gravity  of  1-55.  If  the 
vapor  of  this  compound  is  passed  repeatedly  through  a  tube 
at  a  bright  red  heat,  it  is  decomposed  into  chlorine  and 
C4C18.  This  body  forms  soft,  silky  crystals,  which  are  vola- 
tile and  combustible. 

The  name  of  etlicrilen  has  been  applied  to  the  type  C4H0, 
metameric  with  aceten,  and  etheren  to  olefiant  gas.  The 
derivatives  will  be  monochloricj  bichloric  etheren,  &c. 

Bichloric  etherilen,  by  the  action  of  an  alcoholic  solution 
of  hydrate  of  potash,  yields  chlorid  of  potassium  and  mono- 
chloric  etheren  C4H3C1 :  the  same  way,  trichloric  etherilen 
gives  C3H2C13 ;  and  sexchloric  aceten  C4C16,  with  hydrosul- 
phuret  of  potassium,  yields  C4C14. 

Products  of  the   Oxydation  of  Alcohol. 

736.  Aldehyd  or  Acetol,  C4H4Oa. — The  action  of  oxyd- 
izing  substances    removes   Ha  from    alcohol  and    yields 


PRODUCTS   OP   OXYDATTON   OP   ALCOHOL. 


427 


aldehyd.*  It  is  formed,  together  with  nitrous  ether,  when 
nitric  acid  acts  upon  alcohol.  One  equivalent  of  nitric 

acid  NH06+C4H603=:H203-fNH04-|-C4H402;  besides 
aldehyd,  water  and  nitrous  acid  are  the  products,  the  latter 
of  which  forms  an  ether  with  another  portion  of  alcohol. 
Aldehyd  is  best  obtained  by  the  aid  of  chromic  acid  act- 
ing upon  alcohol.  For  this  purpose  an  apparatus  may  be 
constructed  like  fig.  41 5;  entirely  of  glass,  which  will  bo 


Fig.  415. 

found  very  useful  for  the  distillation  of  numerous  volatile 
products  in  organic  chemistry.  Equal  weights  of  pow- 
dered bichromate  of  potash  and  strong  alcohol  are  introduced 
into  the  flask  a,  and  1£  parts  of  sulphuric  acid  are  gradu- 
ally added  by  the  safety  tube  s.  Much  heat  is  produced 
by  the  mixture,  and  the  distillation  commences  at  once,  but 
is  continued  by  a  gentle  lamp-heat  under  the  sand-bath  of 
a.  .  The  condensing  tube  t  is  of  glass,  and  iced  water  from, 
the  reservoir  n  enters  and  escapes  by  the  two  glass  tubes 
i,  v,  the  former  of  which  has  a  funnel  mouth. 

The   impure  product   is   mixed   with   ether    and   satu- 


*  Whence  its  name,  from  alcohol  deliydrogcnatu*. 


428  ORGANIC   CHEMISTRY. 

rated  with  ammonia,  when  a  compound  of  aldchyd  and 
ammonia  separates  in  fine  crystals.  This,  decomposed  by 
dilute  sulphuric  acid,  affords  pure  aldehyd,  as  a  colorlesa 
liquid  having  a  suffocating  ethereal  odor.  It  boils  at  70°  F., 
and  has  a  specific  gravity  of  -790  :  it  mixes  readily  with 
water,  and,  when  heated  with  a  solution  of  potash,  becomes 
brown  and  deposits  a  resinous  substance. 

The  abstraction  of  H2  seems  to  have  been  made  from  the 
group  C4H5,  and  C2H3  appears  in  acetol  to  play  the  same 
part  as  C4H5  in  alcohol.  Thus,  with  potassium  a  com- 
pound is  formed  which  is  (C4H3.K)02,  and  the  crystalline 
compound  with  ammonia  is  C4H4624-NH3=  (C4H3.NH4)Oa, 
in  which  NH4  replaces  II.  When  a  solution  of  aldehyd  is 
added  to  one  of  ammoniacal  nitrate  of  silver,  the  metal 
is  reduced  and  lines  the  vessel  with  a  brilliant  film  of  sil- 
ver. A  similar  process  has  been  successfully  applied  to  the 
manufacture  of  mirrors. 

737.  Aldehyd  cannot  be  preserved  unchanged,  even  in 
sealed  tubes,  but  is  slowly  changed  into  two  polymeric  com- 
pounds.    One  of  these,  claldchyd,  is  a  dense    oily  fluid, 
which  has  none  of  the  properties  of  aldehyd.     The  density 
of  its  vapor  is  three  times  that  of  aldehyd  ;  and  its  formula 
is  3C4H402  =  C12H13Oq.     The  other  body,  meta Idcliyd,  forms 
hard  white  prisms ;  it  is  formed  by  the  union  of  four  equiva- 
lents of  aldehyd,  and  is  ClflH16Os.     Aldehyd  is  also  ob- 
tained as  a  product  of  the  decomposition  of  lactic  acid  or 
lactate  of  copper  by  heat,  and  is  formed  in  large  quantity 
when  a  lactate  is  distilled  with  binoxyd  of  manganese  and 
sulphuric  acid.     When  the  isomerism  of  lactic  acid  with 
glucose  is  considered,  it  is  easy  to  understand  that  while  the 
latter  is  decomposed  by  fermentation  into  carbonic  acid  and 
alcohol,  lactic  acid  by  oxy elation  may  yield  carbonic  acid 
and  aldehyd.     We  shall  see,  farther  on,  that  it  is  possible 
to  reproduce  lactic  acid  from  aldehyd. 

738.  Chloral* — By  the  prolonged  action  of  chlorine  upon 
alcohol  a  liquid  is  obtained,  to  which  the  name  of  chloral 
has  been  given.     It  is  aldehyd  in  which  chlorine  replacca 
II3,  and  is  represented  by  C4(HC13)02. 

Sulphur  aldehyd  C4H4S3  has  also  been  obtained,  and 
both  the  trichloric  and  sulphuretted  species  yield  polyme- 
ric modifications  similar  to  those  of  normal  aldehyd.  The 
action  of  sulphuretted  hydrogen  upon  an  aqueous  solution 
of  aldchydate  of  ammonia  produces  large  transparent  crys- 


PRODUCTS    OP   OXYDATION    OP   ALCOHOL.  429 

tals  of  an  organic  base,  named  thialdine.  It  is  slightly 
soluble  in  water,  but  dissolves  readily  in  alcohol  and  ether : 
the  crystals  are  very  fusible  and  volatile,  and  may  be  dis- 
tilled with  the  vapor  of  boiling  water.  The  formula  of 
thialdine  a  C13H13NS4 :  it  corresponds  to  an  amid  of  the 
trimeric  modification  of  sulphuretted  aldehyd  C13H13S6. 
This  base  has  no  alkaline  reaction,  but  forms  beautifully 
crystalline  salts.  A  corresponding  compound,  in  which 
selenium  replaces  sulphur,  has  been  formed,  but  is  very 
unstable. 

A  mixture  of  bisulphuret  of  carbon  with  an  alcoholic 
solution  of  aldehydate  of  ammonia  deposits  sparingly 
soluble  crystals  of  a  new  base,  called  carbo-tJiialdine,  which 
is  represented  by  C10H10N3S4.  It  contains  the  elements  of 
two  equivalents  of  aldehyd,  and  its  formation  is  thus  re- 
presented :  2C4H7N09+09S4=2H909+C10H10N9S4. 

739.  Acetic  Add,  C4H404. — When  aldehyd  is  exposed 
to  the  air  it  absorbs  03  and  is  converted  into  acetic  acid 
C4H403-f-02=C4H404.     If  a  mixture  of  hydrate  of  potash 
and  linie  be  moistened  with  alcohol  and  exposed  to  heat, 
hydrogen  gas  is  evolved,  and  an  acetate  formed,  C4H6Oa-|- 
KH03=C4H3K04+H4. 

740.  Pure  alcohol  undergoes  no  change  when  exposed  to 
the  air  alone ;  but  if  its  vapor  mixed  with  air  is  brought  into 
contact  with  platinum-black,  it  slowly  unites  with  oxygen 
to  form  aldehyd,  which  readily  absorbs  another  portion  of 
oxygen  and  produces  acetic  acid.     The  oxydating  power  of 
finely-divided  platinum  has  been  before  alluded  to ;  it  ab- 
sorbs or  condenses  great  quantities  of  gases  and  vapors  in 
its  pores,  where  they  appear  to  be  brought  together  in  such 
a  state  that  they  readily  react  upon  each  other. 

741.  The   formation  of  acetic  acid  may  be  beautifully 
shown  by  placing  a  little  platinum -black  in  a  watch-glass,  by 
the  side  of  a  small  vessel  of  alcohol,  covering  the  whole 
with  a  bell-glass,  and  setting  it  in  the  sunlight.     In  a  short 
time  the  vapor  of  acetic  acid  will  condense  on  the  sides  of 
the  glass,  and  run  down  in  drops;  and  if  we  occasionally 
admit  fresh  air  by  raising  the   bell-jar,  the  whole  of  the 
alcohol  will  be  acidified  in  a  few  hours. 

In  the  ordinary  process  for  vinegar,  alcoholic  liquors,  as 
wine  and  cider,  are  exposed  to  the  air  in  open  vessels. 
Although  a  mixture  of  pure  alcohol  and  water  does  not 
absorb  oxygen  from  the  air,  a  small  portion  of  any  ferment, 


430  ORGANIC   CHEMISTRY. 

as  vinegar,  already  form  ed,  or  the  fun  gus  plan  t 
called  mother  of  vinegar,  enables  it  to  com- 
bine with  oxygen.  In  this  process  the  essen- 
tial thing  is  a  free  supply  of  air  and  a  propel 
temperature.  In  the  manufacture  of  vine- 
gar  on  the  large  scale,  this  is  secured  by 
causing  the  liquor  (b,  fig.  416)  to  trickle  from 
threads  of  cotton  drawn  through  holes,  over 
shavings  of  beech-wood  previously  soaked  in 
Fig.  416.  vinegar,  and  contained  in  a  large  cask  with 
holes  in  its  sides,  (c  c  c  c,)  so  as  to  admit  a  free  circulation 
of  air.  In  this  way  a  vast  surface  is  exposed,  and  the  ab- 
sorption of  oxygen  is  very  rapid,  causing  an  elevation  of 
20°  or  30°  in  the  temperature.  The  liquid  is  passed  through 
this  apparatus  four  or  five  times  in  the  course  of  twenty-four 
hours,  in  which  time  the  change  of  the  alcohol  into  vinegar  is 
generally  complete.  The  product  is  collected  in  the  vessel  a. 

742.  Acetic  acid  is  also  obtained  by  distilling  wood  in 
close  vessels,  (712,)  a  process  employed  on  a  large  scale  for 
the  preparation  of  the  acid.     The  products  are,  besides  car- 
bonic acid  and  carburetted  hydrogen,  a  large  quantity  of 
acetic  acid  mixed  with  oily  and  tarry  matters,  from  which 
it  is  separated  mechanically.     The  acid  thus  prepared  is 
known  as  pyroliyneous  acid,  and  is  largely  used  in  the  arts 
of  dyeing  and  calico-printing ;  but  being  contaminated  by 
cmpyreumatic  oils,  is  not  fit  for  the  purposes  of  domestic 
economy.     By  combining  it  with  bases,  salts  are  obtained, 
which,  when  decomposed,  afford  a  pure  acid. 

743.  By  distilling  dried  acetate  of  soda  with  strong  sul- 
phuric acid,  a  very  concentrated  acid  is  obtained,  which, 
when  exposed  to  cold,  deposits  crystals  of  pure  acetic  acid 
C4H404.     The  pure  acid  is  solid  below  60°  F. ;  when  liquid, 
it  has  a  specific  gravity  of  1-063,  and  boils  at  248°.     It  is 
perfectly  soluble  in  water,  alcohol,  and  ether  ;  it  has  a  pun- 
gent fragrant  odor  and  a  very  acid  taste,  and,  when  applied 
to  the  skin,  is  highly  corrosive.     The  acid  is  monobasic ;  all 
its  salts  are  soluble  in  water. 

Acetates. 

744.  Acetate  of  potash  C4H3(K)04  is  easily  prepared  by 
neutralizing  acetic  acid  with  carbonate  of  potash.     It  is  a 
very  soluble  deliquescent  salt,  and  is  employed  in  medicine. 


ACETATES.  431 

Acetate  of  soda  C4H3(Na)04  forms  large  crystals  with  six 
equivalents  of  water.  It  is  prepared  in  large  quantities  from 
pyroligneous  acid;  the  salt  is  heated  to  destroy  the  oily 
matters,  and  then  affords  by  its  decomposition  a  pure  acid. 
Acetate  of  ammonia  C4H404+NH3  ==  C4H3(NH4)04  is 
used  in  medicine  by  the  name  of  the  spirit  of  Mmdereus. 
It  is  prepared  by  saturating  acetic  acid  with  ammonia,  and 
is  exceedingly  soluble  and  volatile.  The  acetate  of  zinc  is  a 
beautiful  white  salt,  and  is  employed  as  a  tonic  and  astrin- 
gent. The  acetate  of  alumina  C4H3(al)04  is  much  used  in 
dyeing;  it  is  obtained  by  decomposing  a  solution  of  alum  by 
one  of  acetate  of  lead ;  sulphate  of  lead  precipitates,  and 
acetate  of  alumina  with  acetate  of  potash  remains  in  solu- 
tion. The  protacetate  and  pcracetate  of  iron  are  prepared  in 
a  similar  manner,  and  are  largely  employed  in  calico-print- 
ing and  dyeing.  They  are  represented  by  C4(H3Fe)04,  and 
C4H3fe04.  (See  §  649.) 

745.  Acetate  of  Lead,  C4H3(Pb)04.— This  salt  is  well 
known  under  the  name  of  sugar  of  lead.     It  is  prepared  by 
dissolving  oxyd  of  lead  (litharge)  in  acetic  acid,  and  crystal- 
lizes with  three  equivalents  of  water,  which  are  expelled  by 
gentle  heat.     It  is  a  white  salt,  with  a  very  sweet  and  astrin- 
gent taste,  and  is  often  employed  as  a  medicine ;  but  is  poi- 
sonous, and  should  be  used  internally  with  caution. 

The  acetate  of  lead  has  a  great  tendency  to  combine  with 
oxyd  of  lead,  with  which  it  forms  several  definite  compounds. 
These  are  generally  designated  as  basic  salts,  but  should  be 
carefully  distinguished  from  the  salts  containing  more  than 
one  equivalent  of  base,  which  are  formed  by  bibasic  and 
tribasic  acids.  In  these  last,  the  metal  replaces  the  hydro- 
gen of  the  acid,  but  in  the  basic  acetates  the  neutral  salt  com- 
bines directly  with  the  oxyd.  To  distinguish  them,  the  term 
surlasic  is  applied,  and  the  compound  of  the  acetate  with 
an  equivalent  of  oxyd  of  lead  is  called  the  surbasic  acetate 
of  lead.  Three  of  these  compounds  are  known,  in  which 
the  acetate  is  combined  with  one-fourth,  one,  and  two  and  a 
half  equivalents  of  oxyd.  The  second  is  the  only  one  of 
importance. 

746.  Surbasic  Acetate   of  Lead,  C4H3Pb04-fPb3Oa  — 
This  salt,  commonly  called  the  tribasic  acetate,  is  obtained 
by  digesting  a  solution  of  six  parts  of  the  acetate  with  seven 
of  litharge  ;  the  oxyd  is  dissolved,  and  the  liquid  affords,  by 
evaporation,  a  salt  crystallizing  in  long  needles.     It  is  also 


432  ORGANIC   CHEMISTRY. 

slowly  formed  when  metallic  lead  is  digested  in  an  open 
vessel  with  a  solution  of  the  acetate,  oxygen  being  absorbed 
from  the  air.  The  salt  is  very  soluble  in  water,  and  its 
solution  has  an  alkaline  reaction ;  it  is  known  in  pharmacy 
as  Goulard's  extract,  or  solution  of  lead.  When  exposed 
to  the  air,  it  absorbs  carbonic  acid,  and  the  equivalent 
of  oxyd  of  lead  is  precipitated  as  a  carbonate.  This  reaction 
enables  us  to  explain  the  formation  of  white-lead. 

747.  A  process  frequently  employed  is  to  mix  litharge 
and  about  ^3  of  sugar  of  lead  into  a  thin  paste  with  water? 
the  mixture  is  gently  heated,  and  a  current  of  carbonic  acid 
is  passed  through  it.     The  acetate  of  lead  dissolves  a  portion 
of  the  oxyd  to  form  the  tribasic  salt ;  this  is  immediately 
decomposed  by  the  carbonic  acid,  which  precipitates  car- 
bonate of  lead,  and  leaves  the  acetate  free  to  dissolve  a  new 
portion  of  oxyd.     In  this  way  the  smallest  quantity  of  the 
acetate  is  able  to  convert  a  large  portion  of  the  oxyd  into 
carbonate,  and  at  the  end  of  the  process  to  remain  unaltered. 

748.  In  the  ordinary  process,  the  plates  of  lead  are  ex- 
posed to  the  action  of  acetic  acid,  moisture,  air,  and  the  car- 
bonic acid  from  fermenting  tan,  (588.)     The  lead  immedi- 
ately becomes  covered  with  a  film  of  oxyd  by  the  action  of 
the  air.     This  is  dissolved  by  the  vapor  of  the  acetic  acid, 
and  forms  a  solution  of  neutral  acetate,  which  moistens  the 
plates  and  gradually  acts  upon  them,  forming,  by  the  aid  of 
the  atmospheric  oxygen,  the  basic  acetate,  which  is  decomposed 
by  the  carbonic  acid,  in  the  same  manner  as  in  the  last  process, 
and  the  neutral  acetate  is  again  set  free  to  act  upon  the  me- 
tallic lead ;  the  process  goes  on  until  all  the  lead  is  carbon- 
ated.    In  this   way  a  small  quantity  of  acetic  acid  will, 
under  favorable  circumstances,  convert  a  hundred  times  its 
weight  of  lead  into  carbonate  in  a  few  weeks. 

749.  Acetate  of  Copper,  C4H3(Cu)04.— This  salt  is  very 
soluble,  and  forms  beautiful  green  crystals  of  the    monoclinic 
system,  containing  one  equivalent  of  water.     The  acetate  of 
copper  forms  several  surbasic  salts  which  are  insoluble  in 
water.     The  fine  green  pigment  called  verdigris   is  a  mix- 
ture of  two  or  more  of  these :  all  of  these  copper  salts  are 
very  poisonous.     The  acetate  of  silver  C4H3(Ag)04  crystal- 
lizes in  white  scales,  and  is  the  least  soluble  of  the  acetates. 

750.  Chlomcetic  AdJ,  CtCl3(H)04.— We  have  already 
mentioned  this   product    of  the    action    of  chlorine  upon 
crystallizable  acetic  acid ;  one  equivalent  of  the  acid  and 


ACETATES.  43,3 

three  of  chlorine  yield  three  of  chloroliydrie  acid  and 
one  of  the  new  compound,  C4H404-f  3C13==C4C18(H)04 
-f-3HCl.  The  chloracetic  acid  is  very  soluble,  but  may  bo 
obtained  in  fine  rhombohedral  crystals ;  its  salts  resemble 
the  ordinary  acetates.  When  an  amalgam  of  potassium 
is  added  to  a  solution  of  chloracetate  of  potash,  chlorid  of 
potassium,  hydrate  of  potash,  and  the  normal  acetate  of 
potash  are  formed.  In  this  reaction  water  intervenes,  and 
we  may  suppose  that  the  alkaline  metal,  decomposing  water, 
forms  3(KH)Oa  and  3KH,  which  last,  reacting  with  the 
chloracetate,  would  form  chlorid  of  potassium,  leaving  H3in 
place  of  the  chlorine. 

Acetic  Ether,  C4H8(Et)04  =  CgH804.— -This  ether  is  form- 
ed  by  the  direct  action  of  acetic  acid  upon  alcohol,  but  is  best 
obtained  by  distilling  a  mixture  of  five  parts  of  acetate  of 
soda,  eight  of  sulphuric  acid,  and  three  of  alcohol.  It  is  a 
very  fragrant  and  volatile  liquid,  soluble  in  seven  parts  of 
water.  The  odor  of  wine- vinegar  is  due  to  the  presence  of  a 
little  acetic  ether.  It  contains,  like  the  ethers  of  other  mo- 
nobasic acids,  the  elements  of  the  acid  and  the  alcohol  minus 
an  equivalent  of  water  H302.  The  ethers  like  this,  formed  by 
the  acids  of  the  type  Cnllw04  with  their  respective  alcohols, 
are  polymeric  of  the  corresponding  aldeydes ;  acetic  ether 
equals  2  XC4H403.. 

Acetic  ether  is  dissolved  by  a  concentrated  solution  of  am- 
monia, and  the  solution  affords  by  evaporation  a  white  crys- 
talline substance,  very  volatile  and  fusible,  to  which  the  name 
of  acetamid  has  been  given ;  it  is  the  amid  of  acetic  acid, 
and  contains  the  elements  of  acetate  of  ammonia  less  an 
equivalent  of  water :  C4H3(NH4)04  =  C4H?N04  =  H302  -f- 
C4H5NOa,  which  is  the  formula  for  acetamid.  In  its  form- 
ation from  the  ether,  alcohol  is  set  free ;  acetic  ether 
C8H8O4-hNH8=C4H8Oa+C4H5NOfl.  The  ethers  of 
almost  all  acids  yield  amids  by  a  similar  reaction.  When 
heated  gently  with  potassium,  acetamid  evolves  a  gas  and 
yields  cyanid  of  potassium  C3KN. 

If  acetamid  is  distilled  with  anhydrous  phosphoric  acid, 
the  elements  II303  are  abstracted  from  it,  and  a  volatile 
liquid  is  obtained,  which  is  C4H5N03  — II202  =  C4H3N.  It 
has  received  the  name  of  acetonitryl.  By  the  action  of 
strong  acids  and  alkalies  both  of  these  compounds  regenerate 
ammonia  and  acetic  acid. 

751.  When  an  acetate  is  heated  with  an  excess  of  hydrate 


434  ORGANIC   CHEMISTRY. 

of  potash,  it  breaks  up  into  carbonate  of  potash  and  a  sarbo- 
hy drogen  C3H4.  Acetate  of  potash  C4H8K04+  (KH)Ofl  r= 
CaK306-|-C3H4.  It  has  already  been  described  under  the 
name  of  marsh  gas,  from  its  occurrence  in  marshes,  as  a 
product  of  the  decomposition  of  vegetable  matter.  To  indi- 
cate its  relations  in  the  organic  series,  the  name  of  formen 
has  been  given  to  it.  The  chloracetates  undergo  a  similar 
decomposition,  and  yield  trichloric  formen  C3C13H,  in  which 
C13  replaces  H3.  The  chloracetate  of  ammonia  is  decom- 
posed by  boiling  with  an  excess  of  ammonia,  into  carbonate 
and  this  chlorinized  species. 

752.  When  an  acetate  is  decomposed  by  heat,  or  when 
the  vapor  of  acetic  acid  is  passed  through  a  red-hot  tube,  the 
acid  undergoes  a  peculiar  decomposition;  two  equivalents 
of  it  unite  with  the  elimination  of  one  equivalent  of  carbonic 
acid,   C3H300.2  XC4H404=C8H808— CaHaOB  =  C8H6Oa 
To  this  liquid  the  name  of  aceton  has  been  given ;  by  oxyd- 
izing  agents,  like  chromic  acid,  it  yields  acetic  acid.     We 
have  already  mentioned  aceton  as  a  product  of  the  distilla- 
tion of  sugar  with  lime  :  it  is  accompanied  with  an  analogous 
compound,  to  which  the  name  of  metaceton  has  been  given, 
and  which  corresponds  to  a  new  acid  homologous  with  acetic 
acid,  to  which  the  name  of  metacetonic  or  propionic  acid  has 
been  given.     It  is  C6H6O4r=C4H404-t-C2H2,  and  is  very 
much  like  acetic  acid  in  its  properties.     When  a  paste  of 
wheat  flour  is  fermented  with  fragments   of  white  leather 
and  a  quantity  of  chalk,  propionate  of  lime  is  formed  in 
large  quantity.     The  fermentation  is  probably  analogous  to 
that  which  yields  butyric  acid.     The  decomposition  of  the 
salts  of  propionic  acid  by  heat  furnishes  directly  propion  or 
metaceton,  in  the  same  way  as  butyric  acid  furnishes  the 
homologue    butyron.     By  the   action   of   nitric  acid  upon 
butyron,  a  coupled  acid  is  obtained,  which  is  nitropropionio 
acid  C6(H5N04)04=: C8H5N08. 

METHOL,  CaH4Oa. 

753.  Wood-spirit ,  Pyroxylic  Spirit,  Metliylic  Alcohol* — 
This  substance  has  already  been  mentioned  as  a  product  of 

*  Pyroxylic  spirit,  from  pur,  fire,  and  xulon,  wood.  Methylic  alcohol, 
from  methu,  wine,  and  hide,  wood;  signifying  the  wine  or  alcohol  of  wood. 
In  names  like  kakodyl,  and  the  terms  ethyle,  amyle,  in  the  language 
of  the  compound  radical  theory,  the  same  syllable  is  derived  from  hule, 
in  its  more  extended  sense  of  matter  or  principle. 


METHOL.  435 

the  destructive  distillation  of  wood.  The  acetic  acid  of  the 
crude  product  being  saturated  with  lime,  impure  methol  is 
obtained  by  distillation,  and  is  afterward  purified  by  re- 
peated rectifications.  It  is  a  colorless  liquid,  of  a  peculiar 
and  somewhat  unpleasant  odor,  and  a  hot,  pungent  taste. 
It  has  a  specific  gravity  of  -798,  and  boils  at  152° ;  it  ia 
very  combustible,  and  burns  with  a  pale  blue  flame.  Like 
alcohol,  it  mixes  in  all  proportions  with  water.  It  is  occa- 
sionally used  in  the  arts  for  dissolving  resins  and  making 
varnishes,  and  the  pure  wood-spirit  has  lately  acquired 
some  celebrity  in  the  treatment  of  phthisis,  under  the  name 
of  wood-naplitha.  Like  vinic  alcohol,  methol  forms  crystal- 
line compounds  with  several  salts  and  with  baryta.  It 
furnishes  derivatives  in  which  H  is  replaced  by  K,  and 
O3  by  Sfl.  The  nitric  ether  of  methol  is  obtained  by  the 
direct  action  of  the  acid  upon  the  alcohol,  and  resembles 
the  vinic  compound.  The  chlorohydric  ether  CaH3Cl  is  a 
colorless  gas. 

The  hydrobromic  and  hydriodic  methylic  ethers,  ob- 
tained by  processes  similar  to  those  described  for  the  corre- 
sponding vinol  compounds,  are  liquids  at  the  ordinary  tem- 
perature. In  the  bodies  of  this  series,  which  is  homologous 
with  that  of  vinic  alcohol,  C3H3  plays  the  same  part  that 
we  have  assigned  to  C4H5.  This  group  may  be  designated 
by  Me,  and  wood-spirit  will  be  (MeH)03,  while  the  chlorid 
is  MeCl  and  the  nitrate  N(Me)Ofl.  These  ethers  are  decom- 
posed by  a  solution  of  hydrate  of  potash,  with  the  formation 
of  potash  salts  and  methol. 

754.  The  sulpliometliylic  acid  is  prepared  in  the  same 
manner  as  the  sulphovinic;  and  like  it,  is  an  acid  ether. 
It  is  S2(MeH)03.  It  is  more  stable  than  the  sulphovinic 
acid,  and  may  be  obtained  in  crystals.  The  neutral  sulphuric 
ether  is  prepared  by  distilling  wood-spirit  and  sulphuric 
acid,  and  is  Sfl(Mea)Os;  by  boiling  water  it  is  converted 
into  sulphomethylic  acid  and  methol;  Ss(^Mea)08-f-Ha08= 
S2(MeH)08-f  (Mell)  Oa.  With  ammonia  it  undergoes  a 
partial  decomposition,  and  yields  sulphametliane  and  wood- 
spirit;  S3(Me3)08-fNH3--=C3H403+S3(C2H5N)06.  The 
nature  of  the  action  will  be  understood  by  referring  to  what 
has  been  said  of  acetamid  ;  it  is  the  amid  of  sulphoniethylio 
acid,  and  by  hydrate  of  potash  is  decomposed  into  a  sulphate, 
methol,  and  ammonia. 

When  sulphomethylic  acid  is  decomposed  by  heat,  methylia 


436  ORGANIC   CHEMISTRY. 

ether  is  obtained  as  a  colorless  gas.  The  principles  involved 
in  its  formation  are  the  same  as  those  which  have  already 
been  explained  in  speaking  of  the  ether  of  spirits  of  wine. 
Its  formula  is  C4II6Oa  =  MeaOa,  and  it  is  consequently 
metameric  with  vinic  alcohol. 

755.  The  chlorohydric  ether  of  alcohol  has  been  shown 
to  correspond  to  a  carbo'hydrogen  aceten,  C4Ha  =  (C3Ha)3H3 ; 
in  the  same  manner  the  methol  compounds  are  derivatives 
of  a  homologous  hydrocarbon  (C3H3)  H3  =  CaH4,  which  is 
formen  or  marsh  gas,  already  described  as  a  result  of  the 
decomposition  of  the  acetates.  By  the  action  of  chlorine 
the  atoms  of  hydrogen  may  be  successively  replaced,  and 
the  final  result  is  C2C14,  a  chlorid  of  carbon.  The  trichloric 
Bpecies  C2HC13  is  of  some  interest,  and  is  commonly  known 
by  the  name  of  cMoro/brm.  Its  formation  by  the  decompo- 
sition of  chloracetate  of  ammonia  has  already  been  mentioned, 
but  it  occurs  as  a  product  of  the  action  of  chlorine  or  hypo- 
chlorites  upon  many  organic  substances.  When  alcohol  or 
wood-spirit  is  distilled  with  a  solution  of  two  or  three  parts 
of  chlorid  of  lime  in  twenty  of  water,  chloroform  is  the  prin- 
cipal product;  it  is  a  dense  oily  liquid,  having  a  specific 
gravity  of  1480,  boils  at  141°  F.,  and  is  nearly  insoluble 
in  water.  It  has  a  pleasant  aromatic  odor  and  a  very  sweet 
pungent  taste.  An  alcoholic  solution  of  it,  prepared  by  dis- 
tilling chlorid  of  lime  with  an  excess  of  alcohol,  has  long 
been  known  in  medicine  by  the  incorrect  name  of  chloric 
ether.  Its  vapor,  when  mixed  with  atmospheric  air  and  in- 
haled like  ether,  produces  insensibility;  as  it  is  more  agree- 
able to  the  senses  and  more  potent  in  its  operation,  chloro- 
form has,  to  a  considerable  extent,  replaced  ether  as  an 
anaesthetic  agent  in  surgical  practice. 

The  action  of  potash  upon  an  alcoholic  solution  of  iodine 
produces  a  yellow  crystalline  substance,  which  is  iodoform, 
the  iodine  compound  corresponding  to  chloroform,  and  is 
CaHI3.  These  compounds  with  an  alcoholic  solution  of 
hydrate  of  potash  are  decomposed  into  formate,  with  chlorid 
or  iodid  of  potassium,  and  water;  C9HCl8-+-4(HK)Ot=C- 
(HK)04+3KC1+2H303.  The  hydrocarbon  C3H3,  corre- 
sponding to  olefiant  gas,  is  not  known  in  this  series,  but  the 
final  action  of  chlorine  upon  chloroform  produces  C3C14,  which 
is  a  dense  liquid;  at  a  red  heat  it  loses  C13  and  is  converted 
into  a  crystalline  chlorid  C3C13  which  is  the  perchloric  spe- 
cies of  the  unknown  CaHa,  or  perhaps  polymeric  of  it. 


METHOL.  4f7 

Oxydation  of  MetJiol. 

756.  When  the  vapor  of  methol  mixed  with  air,  is  exposed 
to  the  action  of  platinum  black,  oxygen  is  absorbed,  and 
water  is  formed  with  a  new  acid,  which  is  homologous  with 
acetic  acid,  C3H403  -f  04  =  H202  -f  C3H304.      The  inter- 
mediate product   C3H302,  corresponding   to    aldehyd,  has 
never  been  obtained.     The  action  of  heated  hydrate  of  potash 
upon  wood-spirit  evolv7es  hydrogen,  and  forms  a  salt  of  the 
new  acid,  to  which  the  name  of  formic  acid  is  given.     It  is 
Becreted  by  a  species  of  ant,  (Formica  rufa^)  from  whence 
it  derives  its  name,  and  by  the   stinging  nettle,   (Urtica 
urens  ;)  it  is  also  the  result  of  the  action  of  oxydizing  agents, 
upon  many  organic  substances,  as  sugar   and  alcohol,  and 
may  be  advantageously  prepared  by  the  following  process : — 
800  grains  of  bichromate  of  potash  and  300  of  sugar  are 
dissolved  in  seven  ounces  of  water.     The  mixture  is  placed 
in  a  retort,  and  one  measured  ounce  of  sulphuric  acid  very 
gradually  added ;  it  is  then  distilled  (tig.  415)  with  a  gentle 
heat,   until    three  ounces  of  liquid  are   obtained.     This  is 
dilute  formic  acid,  and  may  be  used  to  form  salts,  which, 
when  decomposed,  afford  a  strong  acid. 

The  pure  acid  is  obtained  by  passing  sulphuretted  hydrogen 
gas  over  dry  formate  of  lead ;  sulphuret  of  lead  and  formic 
acid  are  produced.  The  action  is  aided  by  a  gentle  heat, 
and  the  acid  distils  over.  It  is  a  colorless  liquid,  of  specific 
gravity  1-168,  which  boils  at  212°,  and  at  32°  crystallizes, 
like  acetic  acid,  in  shining  plates.  It  fumes  in  the  air,  and 
has  a  very  pungent  odor,  resembling  that  of  ants;  it  is 
powerfully  acid  and  corrosive,  instantly  blistering  the  skin. 
When  this  acid  or  its  salts  are  heated  with  strong  sulphuric 
acid,  it  is  decomposed  with  the  evolution  of  pure  carbonic 
oxyd  gas  :  C3H304  =  C303+H303.  The  formates  resemble 
the  acetates.  The  formate  of  silver  C3(HAg)04  is  decom- 
posed when  its  solution  is  boiled ;  the  silver  is  precipitated, 
while  carbonic  acid  and  carbonic  oxyd  gases  escape, 
2C2(HAg)04  =  Ag3+H303+C204+C303. 

757.  Formic  acid  yields  with  alcohol  an  ether  which  is 
C3(HEt)O4±=08HgO4.      The  acetic    ether   of  methol    has 
the  same  composition  C4(H3Me)04  —  C6H604-     These  two 
ethers  are  similar  in  their  general  physical  characters,  but 
by  the  action  of  hydrate  of  potash,  one  yields  a  formate  and 
alcohol,  and  the  other  an  acetate  and  methol.     The  formic 


438  ORGANIC   CHEMISTRY. 


ether  of  methoi  is  C^HMe^  =  C4TI404  :  it  is  metameric 
with  acetic  acid.  All  of  these  ethers  by  the  action  of  chlorine 
exchange  their  hydrogen  in  whole  or  in  part  for  that  ele- 
ment. The  final  result  of  the  substitution  in  formo-methylic 
ether  is  C4C1404.  We  have  already  shown  that  such  ethers 
are  polymeric  of  the  corresponding  aldehyds.  The  chlorin- 
ized  ether  by  heat  is  resolved  into  two  equivalents  of  phos- 
gene gas  C4C1404  =  2C3C1202  ;  phosgene  gas  is,  in  fact,  the 
chlorinizcd  derivative  of  methylic  aldehyd,  which  will  be 
CaH909. 

AMYLOL,  C10H13Oa. 

758.  Ami/lie  Alcohol.  —  We  have  already  alluded  to  this 
compound  as  a  product  of  fermentation  under  certain  circum- 
stances. In  the  rectification  of  the  crude  spirit  obtained  by 
the  fermentation  of  potatoes,  it  separates  as  an  oil,  which 
comes  over  with  the  last  portions  of  the  spirit,  and  is  inso- 
luble iu  water  :  the  distillers  give  to  it  the  name  of  fouscl 
oil,  or  potato  oil  :  it  is  sometimes  observed  in  the  spirit 
from  other  sources,  and  seems  to  be  a  product  of  the  trans- 
formation of  starch  or  sugar,  under  conditions  not  well 
understood.  When  pure,  it  is  a  colorless  liquid,  which  is 
insoluble  in  water,  has  a  specific  gravity  of  '818°,  and  boils 
at  *2()\)°  F.  It  has  a  burning  taste,  and  a  pungent  odor 
which  excites  coughing  and  often  nausea. 

In  its  chemical  relations  it  is  precisely  similar  to  alcohol, 
and  methoi,  with  which  it  is  homologous  ;  its  formula  is 
C10H1303=(C10HU.H)03;  it  forms  ethers  in  which  C10HM, 
corresponding  to  C2II3,  to  C4II5,  and  to  II,  replaces  hydrogen; 
we  shall  represent  this  group  by  the  symbol  Ayl. 

The  chlorohydric  amylic  ether  is  formed  by  the  action 
of  the  acid  upon  amylol,  and  is  C^II^Cl  =  AylCl.  The 
bromine  smJ  iodine  compounds  are  similar,  as  also  the 
nitrous  and  nitric  ethers,  the  latter  being  N(C10II11)06,  or 
nitric  acid  in  which  Ayl  replaces  hydrogen  ;  as  in  all  similar 
reactions,  H203  is  eliminated  in  its  formation,  and  it  rege- 
nerates a  nitrate  and  amylol  by  the  action  of  an  alcoholic 
solution  of  hydrate  of  potash.  *  With  sulphuric  acid,  sulpha- 
mylic  acid,  corresponding  to  the  sulphovinic,  is  formed,  which 
is  monobasic;  by  its  decomposition,  amylic  ether  C^H^Og 
is  obtained,  which  corresponds  to  the  hydric  ether  of  alcoho1, 
and  is  Ayl202,  or  water  in  which  the  group  C^II^  has  re- 
placed both  equivalents  of  hydrogen.  By  tin  action  of  an 


AMYLOL.  439 

excess  of  sulphuric  acid,  the  carbohydrogen  C^H^,  corre- 
sponding to  olefiant  gas,  is  obtained  :  the  alcohol  breaks  up 
into  C10H10  and  Ha03. 

759.  Oxydation  of  Amylol. — By  the  action  of  platinum 
black,  amylol  combines  with  oxygen  and  is  converted  into 
an  acid  homologous  with  the  acetic  and  formic  acids  :  when 
heated  with  hydrate  of  potash,  hydrogen  is  evolved,  and  a 
salt  of  the  same  acid   is   formed,   C10H1303-j-(KH)03  = 
C10(H9K)04-|-H3.     By  distilling  the  potash  salt  with  sul- 
phuric acid,  the  new  acid  C10H1004  is  obtained.     It  is  iden- 
tical with  that  previously  known  to  exist  in  the  root  of  the 
Valeria na  officinalis,  and  hence  called  valeric  or  valerianic 
add.     It  is  also  found  in  several  other  plants,  and  decay- 
ing cheese  sometimes  owes  its  peculiar  flavor  to  a  proportion 
of  valeric  acid.     It  is  a  colorless  oily  liquid,  which  is  solu- 
ble in  a  large  quantity  of  water,  is  strongly  acid  and  caustic, 
and  has  the  characteristic  odor  of  valerian  root  j  it  boils 
at  347°,  and  has  a  specific  gravity  of  -937.     Its  salts  are  all 
soluble  in  water  and  monobasic ;    they  have  a  slight  odor 
like  the  acid.     The  valerate  of  zinc  crystallizes   in  white 
scales,  and  is  employed  in  medicine  as  a  substitute  for  vale- 
rian, the  medicinal  properties  of  which  it  possesses  in  a  high 
degree.     The  action  of  chlorine  upon  the  acid  alfords  a  pro- 
duct similar  to  chloracetic  acid. 

The  valeric  acid  yields  with  amylic  alcohol  an  ether  which 
has,  when  pure,  an  agreeable  flavor,  like  apples.  The  acetic 
ether  of  amylol  has  a  no  less  striking  resemblance  in  its 
odor  to  jargonelle  pears ;  the  flavors  are  not  however  deve- 
loped until  the  ethers  have  been  diluted  with  alcohol.  These 
ethers  are  obtained  by  distilling  mixtures  of  amylol  and 
acetic  or  valeric  acid  with  sulphuric  acid,  and  are  used  to 
give  the  peculiar  flavors  of  the  fruits  in  perfumery  and  con- 
fectionery. 

760.  In  ascending  the  series  of  alcohols,  in  proportion  as 
the  amount  of  carbon  and  hydrogen  is  greater,  the  bodies 
become  more   insoluble  in  water,  and  assimilated  to  the 
oils  and  fats  and  to  the  different  species  of  wax,  to  which  they 
have  intimate  relations.     These  bodies  are  generally  ethers 
of  acids,  which  are  for  the  most  part  homologous  with  acetic 
and  valeric  acids;  or  glycerids,  a  class  of  compounds  analo- 
gous to  ethers  in  their  composition.     From  them  several 
new  alcohols  are  obtained,  and  a  still  greater  number  of 


440  ORGANIC   CHEMISTRY. 

acids  pertaining  to  the  alcohol  series.  We  shall  first  notice 
those  which  belong  to  the  class  of  compound  ethers. 

Spermaceti. — This  substance  occurs  mixed  with  oil,  fill- 
ing large  cavities  in  the  head  of  the  sperm  whale,  (Physeter 
macrocephalus.)  The  oil  is  removed  by  pressure,  and  finally 
by  washing  in  a  dilute  solution  of  potash,  and  the  sperma- 
ceti is  obtained  as  a  white  solid,  which  fuses  at  120°,  and 
crystallizes  on  cooling  in  beautiful  broad  pearly  plates.  It 
is  soluble  in  alcohol  and  ether,  but  insoluble  in  water,  and 
is  used  in  pharmacy  and  in  the  fabrication  of  candles. 
Spermaceti  has  the  composition  of  a  compound  ether,  and, 
when  gently  heated  with  hydrate  of  potash,  is  decomposed 
into  the  potash  salt  of  a  new  acid  C10(H15K)04,  and  the 
alcohol  of  that  acid  Cl6H1303.  The  acid  has  been  called 
ethalic  add,  and  the  alcohol  ethal  or  ethol ;  spermaceti  cor- 
responds to  the  acetic  acid  of  vinic  alcohol,  and  contains  the 
elements  of  the  acid,  and  the  alcohol  minus  H3Oa.  Both 
of  these  are  white  crystalline  volatile  substances,  analogous 
in  physical  properties  to  spermaceti.  Ethalic  acid  melts  at 
131°;  it  yields  with  other  alcohols,  ethers  which  are  fusi- 
ble and  crystalline.  Ethal  forms  with  sulphuric  acid  the 
sulphethalic  acid,  corresponding  to  the  sulpho vinic,  and  when 
heated  with  hydrate  of  potash  to  400°,  evolves  hydrogen, 
and  is  converted  into  ethalate  of  potash. 

761.  Wax. — This  substance  has  been  supposed  to  be  a 
vegetable  production,  and  to  be  collected  by  bees  from  the 
plants  upon  which  they  feed  ;  but  experiments  have  shown 
that  they  yield  wax  even  when  fed  upon  pure  sugar  or 
honey,  and  that  it  is  a  secretion  of  the  insects  themselves. 

A  species  of  wax  brought  from  China  IK  very  analogous  to 
spermaceti  in  its  composition,  and  when  decomposed  by 
hydrate  of  potash,  yields  the  salt  of  a  new  acid,  called  the 
cerotic,  acid,  and  the  corresponding  alcohol  ccrotoL  The 
acid  has  the  formula  C^H^Oj  and  the  alcohol  is  C^IT^O^ 
These  compounds  are  less  soluble  and  fusible1  than  the 
ethalic  series;  the  wax  fuses  at  18'2°F.,  and  the  alcohol 
at  174°.  The  alcohol  yields  with  sulphuric  acid  a  coupled 
monobasic  acid,  and  with  chlorine  a  product  which  corre- 
eponds  to  a  chlorinized  aldehyd.  Heated  with  hydrate  of 
potash,  cerotol  evolves  hydrogen  and  is  converted  into  cero- 
tate  of  potash.  It  cannot  be  distilled  without  partial  change, 
being  converted  into  water  and  carbohydrogens  polymeric 
with  olefiant  gas. 


GLYCERIDS.  441 

Common  beeswax  is  separated  by  boiling  alcohol  into  a 
soluble  portion,  and  a  residue  comparatively  insoluble.  The 
soluble  part  consists  principally  of  cerotic  acid  in  a  free 
state.  The  insoluble  part  is  decomposed  by  potash  into 
ethalic  acid,  and  a  new  alcohol,  mellisol,  which  is  repre- 
sented by  C8oH6203 :  it  is  crystallizable,  and  melts  at  185°. 
When  fused  with  potash  it  yields  mellisic  acid  C60H6004. 


GLYCERIDS. 

762.  Under  this  title  may  be  included  a  number  of  neutral 
fats  and  oils,  which,  by  the  action  of  bases,  are  converted 
into  salts  of  fatty  acids,  with  the  separation  of  a  substance 
to  which  the  name  of  glycerin  has  been  given,  in  allusion 
to  its  sweet  taste,  (from  glufcw,  sweet.)     Glycerin   is  pre- 
pared by  heating  a  mixture  of  olive-oil,  oxyd  of  lead,  and 
water.    The  oil  is  decomposed,  and  the  acids  form  insoluble 
salts  with  the  lead,  while  the  glycerin  is  dissolved  in  the 
water;  the  solution  is  treated  with  sulphuretted  hydrogen 
to  precipitate  a  little  dissolved  oxyd  of  lead,  and  evaporated 
in  a  water-bath.     It  is  formed  in  large  quantities  as  a  pro- 
duct of  the  saponification  of  fats  by  boiling  with  hydrate 
of  lime  and  water.     The  liquid  which  separates  from  the 
insoluble  lime  salts  is  a  watery  solution  of  glycerin    con- 
taining a  little  lime;  this  may  be  separated  by  carbonic 
acid,  and  the  glycerin  is  then  obtained  by  evaporation. 

The  formula  of  glycerin  is  JC6H806.  It  is  a  colorless, 
syrupy  liquid,  with  a  specific  gravity  of  1-280,  of  a  very 
sweet  taste,  and  is  readily  soluble  in  water  and  alcohol; 
it  is  not  volatile,  but  when  strongly  heated  is  decomposed, 
evolving  acetic  acid  and  other  products,  the  most  important 
of  which  is  acrolein. 

763.  Acrolein  is  also  produced  when  the  glycerids  are 
decomposed  by  heat;  and  is  best  obtained  by  distilling  gly- 
cerin with  anhydrous  phosphoric  acid.     The  glycerin  losea 
the  elements  of  two  equivalents  of  water  :  C8H806 — 2H203  = 
06H403,  which  is  the  formula  of  acrolein.     It  is  a  colorless, 
very  volatile  liquid,  with  a  peculiar  acrid,  penetrating  odor, 
which  is  perceived  when  the  fat  oils  are  strongly  heated  ; 
it  is  lighter  than  water,  and  sparingly  soluble  iu  that  liquid. 
With  potash  it  reacts  liko  aldehyd,  and  it  reduces  oxyd  of 


442  ORGANIC   CHEMISTRY. 

silver  with  the  formation  of  a  new  acid,  the  acrylic,  which 
is  C6H404.  It  resembles  the  acetic  acid  in  its  properties, 
and  under  the  influence  of  alkalies  is  converted  with  oxy- 
dation  into  a  mixture  of  formic  and  acetic  acids ;  C6H404-{- 

2(HK)09+Oa=C4(H3K)04+Cs(HK)C)4+H903. 

764.  The  constitution  of  the  glycerids  is  such,  that  in  de« 
composition  they  combine  with  the  elements  of  3H202,  and 
produce  two  equivalents  of  a  fatty  acid  and  one  of  glycerin. 
All  of  them  undergo  this  change  when  heated  with  a  solution 
of  hydrate  of  potash  or  soda,  or  with  oxyds,  like  oxyd  of  lead 
and  lime.  The  salts  thus  formed  are  soaps;  and  different 
kinds  of  soaps  are  produced,  according  to  the  nature  of  the 
fatty  acid  and  the  alkali.  Those  of  potash  are  very  soluble 
and  remain  mixed  with  the  water,  glycerin,  and  excess  of 
alkali  employed  in  their  preparation ;  they  form  soft  soaps, 
while  those  of  soda  are  less  soluble  and  more  easily  sepa- 
rated from  the  liquid,  and  constitute  hard  soaps.  Those  of 
lime,  lead,  and  other  bases  are  insoluble  in  water,  and  the 
lead-plaster  or  diachylon  of  surgeons  is  a  lead  soap.  When 
a  solution  of  a  soap  with  an  alkaline  base  is  mixed  with  a 
salt  of  any  other  base,  double  decomposition  ensues,  and  an 
insoluble  earthy  or  metallic  salt  is  precipitated ;  it  is  the 
presence  of  salts  of  lime  or  magnesia  in  natural  waters; 
which  gives  them  the  power  of  decomposing  soaps,  and  con- 
stitutes what  is  called  hardness  in  water.  Strong  acids  in 
the  same  way  decompose  soaps,  and  separate  the  fatty  acid 
in  an  oily  form.  Strong  sulphuric  acid  decomposes  the 
glycerids  like  an  alkali,  and  liberates  the  fatty  acids,  form- 
ing with  the  glycerin  an  acid  analogous  to  the  sulphovinic, 
to  which  the  name  of  sulpliogty 'eerie  acid  is  given. 

Butter  consists  of  several  glycerids  which  are  difficult  of 
separation.  When  saponified,  and  the  soap  decomposed  by 
distillation  with  sulphuric  acid,  it  yields  four  volatile  acids, 
homologous  with  the  acetic.  They  are  called  the  butyric, 
caproic,  caprylic,  and  capric  acids.  Of  these  the  first  is 
best  known :  the  others  are  separated  from  it,  and  from  one 
another,  by  the  different  solubility  of  their  baryta  salts. 

Butyric  acid  is  more  easily  obtained  by  the  fermentation 
of  sugar  under  certain  conditions,  which  have  already  boen 
explained,  (700.) 

The  butyrate  of  lime  is  decomposed  by  a  solution  of  car- 
bonate of  soda,  and  the  soda  salt  being  concentrated  by  cva- 


GLYCERIDS.  443 

poration  is  mixed  with  an  excess  of  sulphuric  acid,  when  the 
butyric  acid  rises  to  the  surface  as  an  oily  layer,  which  is 
separated  and  purified  by  distillation.  It  is  a  colorless  liquid, 
which  boils  at  327°  F.,  and  is  lighter  than  water.  It  mixes 
with  pure  water  and  alcohol  in  all  proportions.  The  odor  of 
butyric  acid  is  strong  and  disagreeable,  resembling  that  of  vi- 
negar and  rancid  butter  ;  it  is  powerfully  acid  and  caustic. 
The  salts  of  butyric  acid  are  all  soluble  in  water;  the  buty- 
rate  of  lime  Cs(H7Ca)04  is  less  soluble  in  hot  water  than  in 
cold,  and  separates  almost  entirely  by  boiling,  in  transpa- 
rent prisms,  which  redissolve  as  the  liquid  cools. 

765.  By  mixing  together  alcohol,  butyric  acid,  and  strong 
sulphuric  acid,  the  heat  evolved  is  sufficient  to  cause  the 
formation  of  butyric  ether,  which  is  precipitated  on  adding 
water  to  the  mixture,  being  insoluble  in  it.     It  is  a  colorless 
liquid,  soluble  in  alcohol,  to  which  it  gives  the  flavor  of  pine 
apples;  the  solution  is  used  by  confectioners  to  flavor  syrups, 
and  by  distillers  in  the  fabrication  of  spirits. 

766.  When  a  mixture  of  glycerin  and  butyric  acid  is 
heated  with  sulphuric  acid,  an  oily  liquid  is  obtained,  which 
is  supposed  to  be  the  butyric  glyccrid,  to  which  butter  owes 
its  peculiar  flavor.     It  is  the  only  glycerid  which  has  been 
formed  artificially  ;  by  alkalies  it  yields  glycerin  and  a  buty- 
rate  like  the  natural  glycerids  ;  its  composition,  agreeably  to 
the  rule  which  we  have  stated,  will  be  2CSHS04+C6H806 


The  distillation  of  butyrate  of  lime  affords  butyron  corre- 
sponding to  aceton,  and  a  volatile  liquid,  butyral  C8H802; 
it  absorbs  oxygen  from  the  air,  yielding  butyric  acid,  and  is 
the  aldehyd  of  the  butyric  series. 

The  oil  of  the  porpoise  (Delphinus  phoca)  contains  a  gly- 
cerid, to  which  the  name  of  phocenin  has  been  given  :  it  is 
the  glycerid  of  valeric  acid,  which  has  been  described  by  the 
name  of  phocenic  acid.  The  action  of  nitric  acid  upon  castor- 
oil  yields  a  volatile  oily  acid  with  a  fragrant  odor,  to  which 
the  name  of  enanthylic  acid  has  been  given;  it  is  C14H1404  ; 
and  the  distilled  water  of  the  rose-geranium  (^Pelargonium 
roseuni)  contains  another,  pelargonic  acid,  01SH1804. 

The  peculiar  flavor  or  bouquet  of  wine  is  due  to  a  small 
portion  of  a  peculiar  ether,  which  is  obtained  when  great 
quantities  of  wine  are  distilled,  and  possesses,  in  a  high 
degree,  the  vinous  flavor.  By  hydrate  of  potash  it  is  do- 
composed  into  alcohol  and  a  volatile  acid,  which  has  the 


444  ORGANIC   CHEMISTRY. 

composition  of  pelargonic  acid,  and  is  probably  identical 
with  it. 

The  foregoing  acids  are  all  odorous,  more  or  less  soluble 
in  water,  and  may  be  distilled  over  with  its  vapor;  their 
boiling  points,  however,  become  gradually  higher,  and  their 
lime  and  baryta  salt  less  and  less  soluble.  Beyond  caprio 
acid  C2/)H2004,  they  are  solid  at  the  ordinary  temperature, 
no  longer  volatile  with  the  vapor  of  water,  and  yield  with 
lime  and  baryta  insoluble  salts,  and  with  the  alkalies  proper 
soaps.  Among  these  the  cthalic,  cerotic,  and  melissic  have 
already  been  mentioned.  We  shall  notice  a  few  of  the  more 
important  ones  remaining. 

767.  The  palm-oil  which  is  expressed  from  the  nuts  of 
the  Elais  gurncnsis  is  composed  of  a  fluid  fat,  olcin,  and  a 
solid  crystalline  substance  to  which  the  name  of  palmatin 
has  been  given ;  it  is  the  glycerid  of  ethalic  acid,  which  is 
sometimes  named  palmitic  acid.      The  fat  of  animals  is 
composed  in  like  manner  of  a  liquid  fat  and  a  solid  crystal- 
line material.     By  careful  pressure  in  the  cold,  this  separa- 
tion may  be  in  part  effected,  and  if  the  fats  have  been  kept 
for  a  long  time  in  fusion,  the  solid  portions  crystallize  out 
more  or  less  perfectly  on  cooling.    It  is  by  taking  advantage 
of  this  property  that  lard-oil  is  made.     The  solid  portion 
may  be  purified  by  crystallization  from  ether.      That  ob- 
tained  from  beef  and  mutton  consists   principally  of  two 
substances,  to  which  the   names  of  maryarin  and  stearin 
have  been  given.     The  former  is  readily  soluble  in  ether, 
and   fuses   at    116°  F. ;    stearin,  on  the  contrary,  is  very 
little  soluble  in  cold  ether,  and  melts  at  130°.     By  saponi- 
fication  they  yield  maryaric  and  stearic  acids,  one  fusing  at 
140°,  and  the  other  at  168°.    Although  thus  distinguished, 
these  bodies  have  the  same  composition  :  they  are  both  mo- 
nobasic and  have  the  formula  C34H3404.     The  rnargaric  has 
been  distinguished  by  the  name  cf  para-stcaric  acid.     The 
action  of  heat  and  of  acids  under  certain  conditions  converts 
stearic  acid  into  this  isomeric  modification.     While  marga- 
rin  and  stearin  are  mingled  in  beef  and  mutton  fats,  the 
oils,  like  olive-oil,  consist  of  margarin  and  olein.     Human 
fat  yields  by  saponification  a  large  amount  of  palmitic  acid, 
with  some   margaric,  and  a  new  acid,   which  is  probably 

CS6H3604- 

768.  The  olein  of  lard,  of  olive-oil,  and  of  almond-oil, 

yields  by  saponification  an  acid  which  is  called  oleic  itcid, 


OLYCERIDS.  445 

and,  like  olein  itself,  is  a  colorless  liquid,  insoluble  in  water. 
It  has  a  slightly  acrid  taste,  and  its  alcoholic  solution  has  an 
acid  reaction.  Its  composition  is  represented  by  C3gH3404. 
Oleic  acid  does  not  therefore  belong  to  the  series  of  homo- 
logous acids  already  described,  but  is  one  of  a  new  series, 
of  which  acrylic  acid  C6H404  is  also  a  member;  in  this 
series  the  number  of  equivalents  of  oxygen  is  four,  and  that 
of  the  equivalents  of  carbon  is  always  two  more  than  the 
number  of  the  hydrogen. 

769.  When  the  vapor  of  nitrous  acid  is  passed  through 
oleic  acid,  this  is  rapidly  transformed  into  a  crystalline  sub- 
stance, which  is  elaidic  acid,  and  is  an  isomeric  modifica- 
tion of  the  oleic  acid.    The  action  of  the  nitrous  vapor  upon 
olein  produces  a  corresponding  modification  of  the  glycerid. 
Elaidic  acid,  like  oleic,  is  monobasic,  and  forms  beautiful 
crystals,  which  melt  at  112°.     When  these  acids  are  fused 
with  hydrate  of  potash  they  undergo  a  remarkable  trans- 
formation j  their  homologue,  acrylic  acid,  gives  acetic  and 
formic  acids,  while  the  oleic  and  elaidic  yield  acetic  and 
ethalic  acids  with  the  evolution  of  hydrogen :  C36H3404-{- 
2(KH)03  =  C32(H31K)04+C4(H3K)04+H3. 

The  acid  from  the  saponification  of  a  variety  of  whale-oil 
has  been  found  to  have  the  formula  C38H3604,  and  another 
from  the  vegetable  oil  of  the  Moringia  aptera  C30H3804, 
while  the  olein  from  human  fat  has  yielded  anthropic  add 
C34H3304.  All  of  these  are  monobasic  and  are  homologues 
of  acrylic  acid  and  oleic  acid.  Their  decomposition  by 
hydrate  of  potash  will  probably  yield  corresponding  acids 
of  the  acetic  series.  Thus,  C38H3604,  to  which  the  name  of 
dceglic  acid  ha?  been  given,  should  yield  stearic  and  acetic 
acids. 

770.  Castor-oil  from  the   seeds  of  Ricinus  communis  is 
distinguished  from  other  fixed  oils  by  its  ready  solubility 
in  alcohol.     The  solid  fatty  acids  which  it  yields,  appear  to 
be  margaric  and  palmitic ;    the   olein   affords  by  its  sapo- 
nification an  oily  acid,  which,  while  containing  carbon  and 
hydrogen  in  the  same  proportion  as  in  the  last  series,  has 
six  equivalents  of  oxygen.     Different  experimenters  have 
apparently   obtained   from   different  specimens  of  oil  two 
homologous  acids,  to  which  they  have  ascribed  the  formulas 
C38H3606  and  C36H3406.     To  both  of  these  the  name  of 
ricinoleic  acid  has  been  given.     With  nitrous  vapor,  castor- 
oil  yields  a  crystalline  glycerid  like  olive-oil. 


446  ORGANIC    CHEMISTRY. 

771.  We  have  then  three  homologous  series  among  che 
fatty  acids ;  the  first  and  most  complete  is  that  homologous 
with  acetic  and  ethalic  acids;  the  second  is  that  of  oleio 
acid  ;  the  third  that  of  ricinoleic  acid. 

The  first  has  the  general  formula  CwHn04,  the  second 
C.Hn_204,  and  the  third  CnHM_a06. 

The  series  of  the  first,  as  far  as  known,  is  here  given : — 


1.  Formic CJIa04 

2.  Acetic C4H404 

3.  Propionic C6H604 

4.  Butyric C8H804 

5.  Valoric C10H1004 

6.  Cnproic CwH,a04 

7.  Enanthylic CMHI404 

8.  Caprylic CISIIIS04 

9.  Pclargonic CI8III()04 

10.  Capric C.^II^O, 

11.  Margaritic C^H^O, 

12.  Laurie C24IIa,04 

13.  Cocinic C.Ha.0. 

14.  Myristic C^H^O, 

15.  Benic CIIO 


16.  Ethalic CMTIM04 

17.  Stearic C34II3404 

18.  Bassic C3(.H3K04 

19.  Balenic C^II^O, 

20. 

21. 

22.  Behcnic C^II^O, 

23. 
24. 
25. 
26. 

27.  Ccrotic CMIIH04 

28. 
29. 
30.  Melissic C60IIgo04 


772.  We  have  already  described  the  alcohols  of  the  1st, 
2d,  5th,  16th,  27th,  and  30th  acids,  and  we  have  to  add 
that  of  the  16th.  In  this  group  there  is  a  regular  transition 
rrom  formic  acid,  through  the  propionic,  butyric,  and  other 
paringly  soluble  oily  acids,  to  the  insoluble  ethalic  and 
stearic.  In  the  first  ten,  which  arc  liquid  at  ordinary  tem- 
peratures, and  distil  without  any  change,  there  is  a  progres- 
sive increase  of  about  36°  F.  in  the  boiling  point  of  each 
acid.  Thus,  the  formic  boils  at  212°,  the  acetic  at  212°-f- 
36°  =  248°,  and  the  propionic  at  248°-f  36°  =  284°.  The 
fusing  point  of  the  solid  acids  rises  in  a  similar  manner,  but 
with  less  apparent  regularity. 

The  fact  that  the  acids  are  less  fusible  than  their  glycerids 
has  led  to  their  use  in  the  manufacture  of  candles,  which 
are  sold  under  the  name  of  stearine,  adamantine,  or  Belmont 
sperm.  The  tallow  is  commonly  saponified  by  heating  it  in 
vats  by  steam,  with  a  mixture  of  lime  and  water ;  an  insolu- 
ble lime  salt  is  formed,  and  the  glycerin  remains  dissolved  in 
the  water.  This  salt  is  decomposed  by  diluted  sulphuric 
or  chlorohydric  acid,  with  the  aid  of  heat,  and  the  mixed 
acids,  which  rise  to  the  surface,  are,  when  cold,  submitted 
to  pressure,  by  which  the  oleic  acid  is  removed,  and  the 
stearic  and  margaric  acids  are  obtained  nearly  pure.  The 
crystalline  tendency  of  the  fused  acid  is  corrected  by  adding 


GLYCERIDS.  447 

a  little  pulverized  gypsum  to  tlie  mass  for  the  fabrication  of 
candles. 

The  decomposition  of  the  glycerids  by  sulphuric  acid, 
already  described,  is  sometimes  employed  for  this  purpose. 
The  higher  acids  of  the  series  may  be  distilled  without  change 
in  vacua  or  in  a  current  of  steam,  but  undergo  a  partial  de- 
composition when  distilled  in  the  ordinary  manner.  These 
acids  may  be  distinguished  from  stearin,  from  wax,  and 
spermaceti,  for  which  they  are  often  substituted,  and  with 
which  the  latter  are  frequently  adulterated,  by  their  ready 
solubility  in  alcohol,  and  in  a  heated  solution  of  carbonate 
of  soda. 

773.  The  action  of  nitric  upon  oleic  acid  yields  the  volatile 
acids  of  the  above  series,  from  the  acetic  to  the  capric  inclu- 
sive; the  other  fatty  acids  yield  similar  results,  and  the 
stearic  acid  is  the  first  product  of  the  action  of  nitric  upon 
oleic  acid.     The  residue  of  the  action  of  nitric  acid  contains 
four  soluble  crystallizable  bibasic  acids  —  the  succinic,  CSH008, 
adipicj  C13H1008,  pimelic,  C14Hla08,  and  suberic,  C10H1408  ; 
they  correspond  to  homologues  of  oleic  acid,  which  have  fixed 
04,  and  are  represented  by  CBH,^_aOa.     The  succinic  acid  was 
originally  obtained  by  distilling  amber,  a  fossil  resin  which 
occurs  in  recent  geological  formations.     Succinic  acid  is 
soluble  in  water  and  alcohol  ;  when  heated  it  fuses,  and  is 
decomposed  into  water  and  a  neutral  crystalline  substance 
called  succinid  C8H406,  which,  when  boiled  with  water,  is 
gradually  reconverted  into  succinic  acid.     The  other  acids 
are  of  but  little  importance  ;  the  suberic  is  a  product  of  the 
action  of  nitric  acid  upon  cork.     When  olein  or  oleic  acid 
is  distilled,  selacic  acid  is  obtained  ;  it  is  crystallizable,  vola- 
tile, and  soluble  in  water,  and  has  the  formula  C^H^O,,, 
being  homologous  with  those  just  mentioned.     When  fused 
with  hydrate  of  potash,  these  acids  are  decomposed,  and 
yield  members  of  the  acetic  series.     Thus,  the  pimelic  forms 
valerate  of  potash,  and,  instead  of  the  acetic  acid  and  hydro- 
gen which  the  homologues  of  oleic  acid  would  yield,  carbonic 
acid  and  water  are  obtained. 

774.  Castor-oil  and  ricinoleic  acid,  like  olein,  yield  sebacio 
acid  by  distillation.     When  ricinoleic  acid  is  distilled  with 
an  excess  of  a  strong  solution  of  hydrate  of  potash,  sebacate 
of  potash  is  formed,  and  hydrogen  is  evolved,  with  a  peculiar 
oily  liquid,  having  the  formula  C16H1802.    The  reaction  may 
be  thus  represented  :  C36H3406  +  2(KH)0 


3 


448  ORGANIC   CHEMISTRY. 

-hC16H180?-j-Ha.  The  new  volatile  product  is  the  alcohol 
corresponding  to  caprylic  acid,  and  may  be  named  caprylol. 
It  is  insoluble  in  water,  has  an  agreeable  aromatic  odor,  a 
specific  gravity  of  -823,  and  boils  at  356°  E.  With  sul- 
phuric acid  it  forms  a  vinic  acid,  and  with  acetic  and  chloro- 
hydric acids,  ethers  similar  to  those  of  ordinary  alcohol;  by 
oxydation  it  yields  caprylic  acid  C10H1G04. 

775.  The  different  animal  fats  generally  yield,  by  saponi- 
fication,  small  portions  of  one  or  more  of  the  volatile  acids 
already  described,  and  many  of  them  are  met  with  in  the 
distilled  water  of  various  plants.  Many  glycerids  appear  to 
undergo  a  slow,  spontaneous  decomposition  when  moist; 
glycerin  is  liberated  and  may  be  removed  by  water,  while 
the  acids  are  found  in  a  free  state.  The  alcoholic  ethers  of 
all  these  fatty  acids  may  be  obtained  by  passing  chlorohydric 
acid  gas  through  their  alcoholic  solutions,  or  by  heating  the 
same  solutions  with  sulphuric  acid  :  they  are,  like  the  gly- 
cerids, neutral,  fusible,  fatty  bodies,  and  have  the  same 
constitution  as  their  homologue,  acetic  ether.  When  a  gly- 
cerid  is  dissolved  in  alcohol  and  treated  with  chlorohydric 
acid,  the  ether  is  formed  in  the  same  way,  and  may  be  pre- 
cipitated by  adding  water,  which  will  be  found  to  retain 
glycerin  in  solution.  The  action  of  ammonia  alike  upon 
the  ethers  and  glycerids  enables  us  to  obtain  the  amids  of 
the  fatty  acids  with  the  separation  of  alcohol  or  glycerin. 
They  have  the  same  constitution  as  acetamid,  and  are  all 
decomposed  by  hydrate  of  potash,  with  the  formation  of  a 
salt  of  the  acid  and  ammonia.  Those  of  the  higher  acids 
are  solid  insoluble  fatty  bodies. 


ALKALOIDS  or  THE  ALCOHOL  SERIES. 

776.  The  relations  between  hydrogen  represented  as  H3, 
water,  and  ammonia  have  already  been  considered,  and  we 
have  shown  that  the  alcohols  may  be  viewed  as  compounds  in 
which  the  groups  C2H3,  C4H5,  C10H.UJ  &c.  replace  H  in  water. 
These  same  groups  may  replace  the  successive  equivalents 
of  hydrogen  in  ammonia  and  oxyd  of  ammonium,  giving  rise 
to  an  interesting  class  of  bodies  which  are  perfectly  analo- 
gous to  ammonia  in  their  chemical  relations,  and  are  called 
organic  alkalies  or  alkaloids.  Besides  these  obtained  from 
the  alcohols,  there  are  many  other  alkaloids, products  of  dif- 


ALKALOIDS   OF   THE   ALCOHOL   SERIES.  449 

ferent  transformations  of  organic  bodies 5  others  exist  ready 
formed  in  plants.  We  shall  in  this  place  consider  only 
the  first  class. 

777.  When  chlorohydric,  or  better  bromohydric  ether,  is 
digested  with  a  concentrated  solution  of  ammonia,  it  slowly 
dissolves.     This  operation  is  accelerated  by  heat,  and  is  best 
effected  by  exposing  the  ether  and  ammonia  hermetically 
sealed  in  glass  tubes,  to  the  heat  of  boiling  water.    The  solu- 
tion is  soon  effected,  and  the  mixture,  on  cooling,  is  found 
to  contain  a  salt  of  the  new  ether-ammonia :  hydrobromic 
ether,  EtBr-f  NH3=NH3Et.Br,  bromid  of  ethammonium, 
or  NH3Et.HBr.     When  decomposed  by  lime  or  potash  in 
the  same  way  as  sal-ammoniac,  the  new  alkaloid  NH3Et, 
which  is  named  ethamine,  is  obtained  as  a  very  volatile 
liquid,  with  a  specific  gravity  of  -696.     It  has  a  powerful 
odor  resembling  that  of  ammonia,  and  its  solution  is  very 
caustic,  acting  like  a  strong  alkali  with  acids  and  metallic 
gaits.     It  is  soluble  in  all  proportions  in  water  and  alcohol. 

778.  If  a  hydracid  ether  of  methol  be  substituted  for  the 
vinic  ether,  a  corresponding  methylic  ammonia,  or  metha- 
mine,  may  be  obtained,  which  is  NH3(CaH3)  or  NHaMe. 
It  is  a  colorless   gas,   which  at  a  low   temperature   may 
be  condensed  into  a  liquid,  and  is  very  soluble  in  water, 
which  dissolves  in  the  cold  1154  times  its  own  volume  of 
the  gas.     The  solution  is  powerfully  acrid  and  caustic,  and 
in  its  odor  and  chemical  properties  closely  resembles  am- 
monia; the  gas  is  combustible.     The  salts  of  these  new 
bases  are  like  those  of  ammonia,  but  are  more  soluble. 

When  placed  in  contact  with  a  new  equivalent  of  the 
ether,  these  alkalies  react  with  it  precisely  like  ammonia 
itself,  and  salts  of  new  alkaloids  are  obtained,  in  which  two 
and  three  atoms  of  hydrogen  are  successively  replaced  by 
the  carbohydrogen  elements.  In  this  way  NHEt3  and 
NEt3  =  NC13H15  arQ  obtained;  and  by  using  successive  dif- 
ferent ethers,  mixed  alkaloids  may  be  formed,  such  as 
NHEtMe  and  NMe3Et.  The  amylic  and  cetylic  ethers  yield 
perfectly  analogous  compounds.  Amylamine  is  NH3Ayl  — 
NHfi(C10H11).  It  is  a  very  mobile  liquid,  having  a  specific 
gravity  of  -750,  and  boiling  at  203°  ;  it  has  at  the  same  time 
the  odor  of  ammonia  and  of  the  amylic  compounds,  and  is  very 
caustic  and  alkaline.  We  may  even  have  N(Me.Et.Ayl),  in 
which  the  elements  of  three  different  alcohols  are  united. 
These  higher  alkaloids  are  liquids,  which  have  still  the  ch»- 

29 


450  ORGANIC    CHEMISTRY. 

racters  of  ammonia,  but  are  less  volatile  and  caustic  than  those 
of  lower  equivalents. 

779.  When  triethamine  NEfc3  is  brought  in  contact  with 
another  equivalent  of  hydriodic  ether,  it  no  longer  decom- 
poses it,  but  unites  directly  with  it  to  form  a  salt.     This 
ether  EtI,  as  we  have  already  shown,  corresponds  to  HI, 
and  the  ammonia  unites  with  it  as  it  would  with  the  acid: 
in  the  latter  case  a  simple  ammonia  would  form  iodid  of 
ammonium  NH4I,  and  the  trivinic  ammonia  N(Et,H)I;  but 
with  the  ether  it  forms  NEt3.EtI  =  NEt4I,  or  the  iodid  of 
vinic  ammonium  NEt4.      The  new  iodid  forms  fine  crystals, 
which  have  all  the  reactions  of  an  ordinary  iodid  with  me- 
tallic salts.    With  recently  precipitated  oxyd  of  silver,  double 
decomposition  ensues,  giving  rise  to  iodid  of  silver  and  oxyd 
of  vinic  ammonium:  2NEt4I-fAgsOa==2AgI+(NEt4)909j 
but   as   anhydrous   lime  with  water   produces   a   hydrate 
(CaH)03,  so  the  new  oxyd  forms  with  it  two  equivalents 
of  a  hydrate  (NEt4.H)0,,,  which  corresponds  to  (KH)02. 
It  is  obtained  by  evaporation  as  a  very  soluble,  deliquescent 
substance,  alkaline  and  corrosive   like  hydrate   of  potash, 
which  it  closely  resembles  in  its  chemical  reactions.    As  we 
have  supposed  ammonia  to  unite  with  water  and  form  a 
hydroxyd  of  ammonium,  so  in  this  compound  the  trivinic 
ammonia  is  united  with  vinic  water  or  alcohol.    The  aqueous 
compound  of  ammonia  is  readily  decomposed  by  heat;  and 
in   like  manner,  if  the  new  oxyd  is  exposed   to  the  heat 
of  boiling  water,  it  is  decomposed  into  trivinic  ammonia, 
and  alcohol,  which  latter  breaks  up  into  olefiant  gas  and 
water;  C4H4-f-H303. 

780.  The  methylic  compound  is  quite  similar  to  the  last. 
When  the  hydriodic  ether  of  methol  is  digested  with  ammo- 
nia, the  hydriodate  of  methamineisfor  the  most  part  trans- 
formed into  the  iodid  of  ammonium,  and  the  iodid  of  niethic 
ammonium;  4N(H3Me)I=3NH4I-f  N(Me4)L     The  new 
iodid  forms  sparingly  soluble  crystals,  which  yield  a  hy- 
droxyd very  alkaline  and  caustic. 

The  amylic  and  complex  ammonium  salts  are  analogous  in 
their  characters.  Ethamine  andmethamine  have  \  een  obtained 
by  several  other  processes,  and  are  found  in  the  products  of 
animal  decomposition. 

781.  By  the  action  of  an  alloy  of  potassium  and  antimony 
upon  the  hydriodic  ethers,  compounds  are  obtained  represent- 
ing ammonias,  in  which  aiitimony  replaces  nitrogen,  (645.) 


ALKALOIDS   OP   THE   ALCOHOL  SERIES.  451 

They  are  SbMea=SbCBH9  and  SbEt3  =  SbC13HJ5.  By 
oxydizing  agents  they  lose  H2,  and  the  resulting  compounds 
constitute  alkaloids  which  form  a  class  of  salts. 

Stibethic  ammonia  unites  with  hydriodic  ether  to  form 
SbEt4.I,  analogous  to  the  nitrogen  compound,  and  this,  with 
oxyd  of  silver,  yields  a  hydroxyd  which  is  a  strongly  alka- 
line base.  In  like  manner,  SbMe4I  and  Sb(Me3Et)I  may  be 
obtained ;  all  corresponding  to  the  iodids  of  ammonium  and 
potassium.  The  action  of  chlorine  or  nitric  acid  upon  sti- 
bethic  ammonia  removes  H2  and  gives  rise  to  salts  of  a  new 
alkaloid  SbC12H13,  which  is  called  stibethine. 

782.  When  a  mixture  of  acetate  of  potash  and  arsenious 
acid  is  distilled  at  a  low  red  heat,  there  is  obtained,  among 
other  products,  a  volatile  liquid,  somewhat  soluble  in  water, 
to  which  the  name  of  alkarsine  has  been  given.     It  is  an 
organic  base,  related  to  those  just  described,  in  which  arsenic 
replaces  nitrogen.     It  contains  CsH13As202,  and  corresponds 
to  the  oxyd  of  an  arsenic  ethamine,  from  which  H2  has  been 
eliminated,  as  in  stibethine ;  As(EtH2)  =  AsC4H7  —  H2  =  As 
C4H5,  which  combines  with  chlorohydric  acid  like  ammonia : 
the  anhydrous  oxyd  (AsC2H5)2.H203  =  (AsC3Hfl)203  is  al- 
karsine, or  oxyd  of  arsinum.  With  chlorohydric  acid  it  yields 
a  liquid  chlorid  (As03H6)Cl,  to  which  the  name  of  chlorarsine, 
or  chlorohydrate  of  arsine,  has  been  given.    It  is  a  true  salt, 
like  chlorid  of  ammonium,  and  by  double  decomposition  yields 
different  salts,  which  are  also  formed  by  the  action  of  acids 
upon  alkarsine.     The  chlorid  is  decomposed  by  metallic  zinc; 
chlorid  of  zinc  is  formed,  and  the  organic  elements  are  set 
free ;  but  two  equivalents  of  arsinum  unite  to  form  a  com- 
pound, which  is  C8Hlj.Asa=(AsCaH6)fl.     It  is  a  compound 
quasi-metal,  and  corresponds  to  Zn2  and  H2.     It  combines 
directly  with  chlorine  to  form  anew  the  chlorid  \  like  alkar- 
sine, it  is  a  volatile  liquid,  which,  when  exposed  to  the  air, 
fumes  and  takes  fire  even  at  the  ordinary  temperature.    All 
of  these  compounds  have  a  disgusting  odor,  and  are  fear- 
fully poisonous.    The  oxyd,  alkarsine,  is  like  an  alkali,  acrid 
and  corrosive.     M.  Bunsen,  to  whom  we  are  indebted  for  a 
knowledge  of  these  bodies,,  gave  to  the   compound  quasi- 
metal  the  name  of  Italwdyl,  (from  kakosj  evil,  and  huh, 
principle.) 

783.  When  kakodyl  is  covered  with  water,  it  slowly  ab- 
sorbs oxygen  from  the  air  and  yields  alkarsine  :  if  to  the 


452  ORGANIC   CHEMISTRY. 

alkarsine/oxyd  of  mercury  is  added  under  water,  the  metallic 
oxyd  is  reduced,  and  a  new  compound  remains  in  solution, 
formed  by  the  oxydation  of  the  alkaloid  arsine,  which  com- 
bines with  the  oxygen  and  forms  AsC4H504,  which  is  the 
formula  of  the  new  body,  alkargen.  The  solution  yields 
by  evaporation  large  rhombic  prisms  of  the  new  substance, 
which  is  inodorous,  has  but  little  taste,  and  is  not  at  all 
poisonous.  Deoxydizing  agents,  like  sulphurous  acid,  converts 
it  into  alkarsine.  Alkargen  combines  with  acids  to  form 
crystalline  compounds  like  arsine;  but  by  its  combination 
with  oxygen  the  alkaloid  seems  to  have  become  more  feebly 
basic  than  before ;  as  in  ammonia,  one  atom  of  hydrogen  in 
alkargen  or  its  salts  is  replaceable  by  a  metal,  so  that  we 
may  have  a  compound  like  AsC4(H4Cu)04.HCl,  or  chloro- 
hydrate  of  cupric  alkargen.  By  the  action  of  sulphuretted 
hydrogen,  the  oxygen  in  this  alkaloid  is  replaced  by  sulphur, 
and  crystals  obtained  which  are  AsC4H.S4. 

784.  Succeeding  the  alcohols  and  their  derivations  may 
be  considered  a  class  of  volatile  liquids,  many  of  them  essential 
oils,  which  have  analogies  with  alcohols  or  aldehyds,  although 
not  homologous  with  the  preceding  series.    We  shall  men- 
tion briefly  some  of  the  more  important.     Their  history  is 
now  nearly  as  complete  as  the  alcohols,  and  scarcely  less  in- 
teresting, but  the  limits  of  this  work  will  not  permit  us  to 
speak  of  them  at  length. 

BITTER-ALMOND  OIL,  C14HB03. 

785.  Bcnzoilol,  Essential  Oil  of  Bitter  Almonds. — This 
oil  does  not  exist  ready  formed  in  the  almonds,  but  is  pro- 
duced by  the  reaction  of  certain  principles  contained  in  the 
kernel,  when  aided  by  the  presence  of  water.     It  is  obtained 
by  bruising  bitter  almonds  into  a  paste  with  water,  and  dis- 
tilling the  mixture,  when  the  oil  passes  over,  with  hydro- 
cyanic acid  and  other  impurities-     It  is  purified  by  redistil- 
ling it  from  a  mixture  of  protochlorid  of  iron  and  lime,  and 
is  a  colorless  oily  liquid,  of  a  pungent  burning  taste,  and 
very  fragrant  odor,  like  that  of  bruised  bitter  almonds.     It 
boils  at  356°,  but  its  vapor  distils  over  with  that  of  water 
at  212°  :  its  specific  gravity  is  1-073.      It  is  often  used  in 
flavoring  articles  of  food,  but  the  crude  oil  which  is  sold  for 


BENZOILOL.  453 

this  purpose  is  exceedingly  poisonous ;  the  pure  oil  is  com- 
paratively harmless. 

By  the  action  of  hydrosulphuret  of  ammonia  upon  bit- 
ter-almond oil,  its  oxygen  is  replaced  by  sulphur,  and  an 
insoluble  powder  is  obtained  of  the  formula  C14H6S3.  Its 
decomposition  by  heat  gives  rise  to  a  variety  of  new  and 
curious  products. 

786.  Vhlorinized  Benzoilol,  C14H5C102.— This  is  obtained 
by  the  action  of  dry  chlorine  gas  upon  the  oil  of  bitter 
almonds.     It  is  a  colorless  liquid,  which  is  decomposed  by 
alkalies,  yielding  a  chlorid  and  a  benzoate.     By  distilling 
this  with  bromid  or  iodid  of  potassium,  similar  compounds 
are  obtained,  in  which  bromine  or  iodine  replaces  an  equiva- 
lent of  hydrogen. 

The  action  of  dry  ammonia  upon  the  chlorinized  ben- 
zoilol  yields  chlorohydric  acid,  and  a  new  substance,  benza- 
mid,  C14H5C103+NH3^C14H7N03+HC1.  It  is  soluble 
in  water,  and  crystallizes  in  beautiful  prisms. 

787.  Hydrobenzamid. — When  bitter-almond  oil  is  placed 
in  a  concentrated  solution  of  ammonia,  it  is  gradually  con- 
verted into  a  white  crystalline  mass  of  this  substance.     It 
is  formed  from  three  equivalents  of  benzoilol  and  two  of 
ammonia  by   the   abstraction   of    the   elements    of  three 
equivalents  of  ^  water;  _  3(C14H6O2)-f  2NH3  =  C43H18N2  + 
3H3Oa.     In  this  reaction  the  ammonia  loses  the  whole  of 
its  hydrogen,  which  unites  with  the  oxygen  of  the  oil,  and 
the  residue  (Na)  is  substituted  for  06.     By  the  action  of 
chlorohydric  acid  it  takes  up  the  elements  of  water,  and 
regenerates    the   oil    and   ammonia ;  the    latter    combines 
with    the  acid   to  form  sal-ammoniac.       When  boiled  in 
a   solution  of  potash,  it   is  converted   into   a   metameric 
modification,  which  is  no  longer  decomposed  by  acids,  but 
unites   directly  with   them  and   neutralizes    them.      This 
substance,  which  is  an  alkaloid,  is  also  formed  when  ammo- 
nia is  passed  through  an  alcoholic  solution  of  the  oil  of 
bitter  almonds ;  it  is  called  benzoline  or  amarine. 

When  the  crude  oil  of  bitter  almonds  is  mixed  with  an 
alcoholic  solution  of  potash,  it  is  gradually  converted  into  a 
white  crystalline  substance,  which  is  called  benzoine.  It  is 
polymeric  of  the  oil,  and  is  formed  by  the  union  of  two 
equivalents  of  it;  its  formula  is  consequently  C2SH1204. 
When  the  vapor  of  benzoine  is  passed  through  a  red-hot 


454  ORGANIC    CHEMISTRY. 

tube,  it  is  reconverted  into  bitter-almond  oil.  By  the  action  of 
chlorine  upon  fused  benzoine,  H3  is  removed  in  the  form  of 
2HC1,  and  a  crystalline  compound  remains,  which  is  called 
benzile,  and  is  C28H1004. 

788.  When  bitter-almond  oil  is  exposed  to  the  air,  it 
rapidly  absorbs  oxygen,  and  is  converted  into  a  white  crys- 
talline substance,  which  is  benzoic  acid ;  this  is  formed  by 
the  combination  of  two  atoms  of  oxygen ;  the  oil  is  the 
aldehyd  of  the  acid.  The  same  effect  is  produced  when 
the  oil  is  heated  with  hydrate  of  potash  ;  hydrogen  gas  is 
evolved,  and  benzoate  of  potash  formed.  A  more  abun- 
dant source  of  benzoic  acid  is  found  in  benzoin,  a  fragrant 
resinous  substance  which  is  obtained  from  the  Laurus  ben- 
zoin. This  contains  a  large  quantity  of  the  acid,  which 
may  be  procured  by  exposure  to  a  gentle  heat,  when  the  acid 
is  volatilized,  and  condenses  as  a  white  sublimate.  It  is 
also  obtained  by  boiling  the  benzoin  with  lime,  which  forms 
benzoate  of  lime  j  chlorohydric  acid  added  to  the  previously 
concentrated  solution,  precipitates  the  pure  acid  in  crystal- 
line plates.  Benzoic  acid  forms  light  silky  crystals  of  a 
pearly  whiteness,  and  has  a  pleasant  aromatic  taste,  very 
slightly  acid.  When  pure  it  is  inodorous,  but  generally 
has  a  little  volatile  oil  adhering  to  it,  which  gives  it  a  fra- 
grant odor,  like  vanilla.  It  is  volatile  at  a  gentle  heat,  evolving 
a  suffocating  vapor,  which  condenses  unchanged.  It  is  very 
slightly  soluble  in  cold,  but  more  easily  in  hot  water. 

The  formula  of  benzoic  acid  is  C14H004 :  it  is  monoba- 
sic, and  forms  a  large  class  of  salts,  which  are  of  but  little 
importance.  The  benzoic  vinic  ether  is  obtained  by  pass- 
ing chlorohydric  acid  gas  through  an  alcoholic  solution  of 
beuzoic  acid,  and  is  C14(H5Et)04  —  C1?H1004.  It  is  a  fra- 
grant volatile  liquid,  which  in  its  chemical  reactions  resem- 
bles the  other  ethers  j  with  ammonia,  it  affords  benzainid 
and  alcohol.  Benzamid  is  the  amid  of  benzoic  acid,  and 
with  H203  yields  benzoic  acid  and  ammonia.  It  is  vola- 
tile, but  at  a  high  temperature  loses  a  second  equivalent  of 
H20a  and  becomes  C14H5N.  This  is  a  liquid  to  which  the 
name  of  benzonitryl  is  given  •  with  2H203  it  regenerates 
benzoic  acid  and  ammonia. 

With  strong  nitric  acid,  benzoic  acid  yields  a  crystalline 
compound,  with  the  elimination  of  H302 ;  it  is  the  nitro- 
benzoic  acid  which  has  already  been  alluded  to,  (652,)  and 
from  its  mode  of  formation  is  monobasic.  When  heated 


PHENOL.  455 

with  a  mixture  of  nitric  and  sulphuric  acids,  a  second 
equivalent  of  nitric  acid  is  fixed,  and  binitrobenzoic  acid  is 
formed. 

The  atom  of  hydrogen  in  each  case  is  eliminated  from 
the  nitric  acid,  and  its  saline  capacity  destroyed,  but  the 
benzoic  elements  still  retain  the  original  atom  of  H, 
replaceable  by  a  metal,  and  thus  each  of  the  new  acids  is 
monobasic.  The  decompositions  of  the  ethers  and  amids 
of  these  acids  yield  a  variety  of  curious  compounds. 

789-  Benzen. — The  vapor  of  benzoic  acid  passed  through 
a  red-hot  gun-barrel,  is  decomposed  into  carbonic  acid  and  a 
new  substance  named  benzen,  benzol,  or  phene,  which  is 
C13H6.  C14Hfl04=C304-}-C13H8.  Benzen  is  more  easily 
obtained  by  distilling  benzoic  acid  with  slaked  lime,  which 
combines  with  the  carbonic  acid.  It  is  a  colorless,  fragrant 
liquid,  which  boils  at  187°,  and  has  a  specific  gravity  of 
•830 ;  at  .32°  F.  it  forms  a  white  crystalline  mass.  Ben- 
zen is  formed  when  the  fat  oils  are  decomposed  at  a  red 
heat,  and  is  obtained  in  the  manufacture  of  oil-gas  for  illu- 
mination. With  fuming  sulphuric  acid,  benzen  yields  a 
monobasic  acid,  the  sulphobenzenic,  and  a  neutral  crystalline 
body,  mlplwbenzid.  They  are  analogous  to  sulphovinic  acid 
and  sulphuric  ether. 

The  phenic  alcohol  or  phenol  C13H603  is  obtained  by  the 
decomposition  of  salicylic  acid,  which  contains  two  atoms 
more  of  oxygen  than  benzoic  acid.  The  name  of  carbolic 
acid  is  also  given  to  it,  and  it  occurs  as  a  natural  product 
in  the  secretion  of  the  beaver,  called  castor enm,  which  owes 
its  peculiar  odor  and  probably  its  medicinal  properties  to  a 
small  portion  of  phenol  j  it  is  also  contained  in  the  oil  of 
coal-tar.  Phenol  forms  colorless  crystals,  which  are  liqui- 
fied by  moisture,  although  but  slightly  soluble  in  water. 
Its  aqueous  solution  has  an  acrid  taste,  and  an  odor  like 
wood-smoke  or  cfeasote,  which  it  also  resembles  in  being 
poisonous,  and  a  powerful  antiseptic.  Kreasote  is  probably 
an  homologue  of  phenol. 

790.  The  derivatives  of  phene  and  phenol  may  be  repre- 
sented as  compounds  in  which  C13H5  replaces  H,  precisely 
as  the  group  C4HS  in  those  of  vinic  alcohol.  With  sulphu- 
ric acid,  phenol  yields  phenosulphuric  acid  Sa(C13H5.H)Og! 
That  formed  by  benzen  is  S3(C13HS.H)0B,  and  is  pheno- 
sulphurous  acid:  sulphurous  "acid",  2(SOa.HO)  =  S3H300. 
With  nitric  acid,  phenol  yields  three  successive  products,  in 


456  ORGANIC    CHEMISTRY. 

which  one,  two,  and  three  equivalents  of  N04  may  oe  r3« 
presented  as  replacing  hydrogen.  The  view  of  tbo  con- 
stitution of  such  bodies,  given  under  nitrobenzoic  acid,  is, 
however,  to  be  preferred.  Phenol  has,  like  abohol,  an 
atom  of  hydrogen,  replaceable  by  a  metal,  and  all  these 
derived  compounds  have  acid  characters  and  are  mono- 
basic. The  trinitric  phenol  is  interesting  as  the  final  re- 
sult of  the  action  of  nitric  acid  upon  many  organic  sub- 
stances, and  has  been  described  under  the  names  of  picric, 
nitropicricj  carbazotic,  and  nitrophenisic  acids.  It  18 
CiaH3(NOJ3Oa==C18H8N3p14,  and  forms  yellowish-white 
crystalline  scales,  which  dissolve  in  a  large  quantity  of 
water,  yielding  a  deep-yellow  solution,  with  an  intensely 
bitter  taste.  Its  salts  are  yellow,  and  explode  when  heated. 
That  of  potash  C12(H2K)N3014  is  a  crystalline  salt,  very 
sparingly  soluble  in  water. 

791.  The  action  of  nitric  acid  upon  benzen  yields  a  dense 
oily  liquid,  which  has  a  very  sweet  taste,  and  an  odor  like  the 
essence  of  bitter  almonds,  for  wbich  it  is  substituted  in  per- 
fumery. It  contains  C12H5N04,  and,  by  the  further  action 
of  a  mixture  of  nitric  and  sulphuric  acid,  fixes  a  second 
equivalent  of  the  nitrous  elements,  and  yields  C13H4N308. 
Nitrobenzen  is  to  nitrophenol  what  nitrous  ether  is  to  nitric 
ether,  and  is  the  nitrous  ether  of  phenol,  or  N(C13H5)04  = 
C13H5N04,  and  the  second  product  may  be  regarded  as 
N(CiaH5.N04)04,  still  corresponding  to  N(H)O4. 

79*2.  Phenol  combines  with  ammonia  and  forms  C13H602, 
NH3.  When  this  compound  is  heated  in  a  sealed  tube,  it 
is  converted  into  water,  and  a  new  alkaloid:  C?3H602-f- 
NH3==H3034-C13H7N.  This  is  an  ammonia  in  which 
C13H5  replaces  H,  and  is  N(C12H5.H2).  The  same  group 
may  replace  an  atom  of  hydrogen  in  the  alcohol-ammonias, 
and  mixed  ammonias  containing  the  different  alcoholic  and 
phenic  carbohydrogens,  are  thus  obtained.  To  this  new 
alkaloid  the  name  of  aniline  is  given  :  it  is  a  colorless,  oily 
liquid,  with  a  pleasant  vinous  odor,  a  burning  taste,  and  is 
poisonous  :  it  boils  at  328°,  and  has  a  specific  gravity  of 
1-028.  Aniline  is  slightly  soluble  in  water;  it  decomposes 
metallic  solutions,  and  with  acids  acts  the  part  of  a  strong 
alkali,  forming  crystalline  salts.  These  salts  by  heat  yield 
compounds  analogous  to  the  amids,  which  are  called  aniluh. 
They  are  amids  in  which  C12H5  replaces  H.  The  presence 
of  aniline  is  readily  detected  by  a  solution  of  hypochlorito 


ANILINE.  457 

of  lime  or  bleaching-powder,  which  produces  a  beautiful 
violet-blue  with  a  solution  of  the  alkaloid.  It  occurs  as  a 
product  of  the  destructive  distillation  of  many  organic 
matters,  and  is  associated  with  phenol  in  coal-tar. 

When  an  alcoholic  solution  of  nitrobenzen  is  mixed 
with  sulphuric  acid  and  a  fragment  of  zinc,  the  hydrogen 
evolved  by  the  decomposition  of  the  acid  reacts  with  the 
nitrobenzen  to  form  aniline  and  water,  C12H5N04-{-3Ha  = 
C12H7N-|-2H303.  Sulphuretted  hydrogen  produces  a  similar 
effect,  sulphur  being  separated.  When  binitric  benzen  is 
thus  treated,  an  alkaloid  is  obtained,  which  is  nitric  aniline, 
in  which  one  equivalent  of  the  nitric  elements  enters 
into  the  alkaloid;  it  is  C12H6(N04)N. 

By  indirect  processes,  alkaloids  are  obtained  which  corre- 
spond to  aniline,  in  which  H  and  H2  are  replaced  by  chlorine 
and  bromine.  Their  basic  powers  are  less  strong  than  the 
normal  aniline,  and  the  trichloric  species  C13H4C13N  is  no 
longer  an  alkaloid.  When  by  double  decomposition  we 
endeavor  to  obtain  a  hyponitrite  of  aniline,  the  salt  is  at 
once  decomposed  into  phenol,  nitrogen  gas,  and  water, 


798.  When  benzoate  of  lime  is  submitted  to  distillation, 
the  principal  product  is  a  body  corresponding  to  the  aceton 
of  acetic  acid  j  two  equivalents  of  benzoate  2C14(H5Ca)04  = 
CaCa^Og-f-CagH^Oa.  The  new  compound  is  fusible,  volatile, 
and  crystallizes  in  large  prisms,  which  are  soluble  in  alco- 
hol and  ether  ;  fused  with  hydrate  of  potash,  it  is  decom- 
posed into  benzoate  and  benzen,  C30H10Oa-f  (KH)02== 
C14(H6K)04-|-C12H6.  From  this  relation  to  benzoates  and 
benzen  or  phene,  it  has  received  the  name  of  benzophenon  : 
with  chemical  agents  it  affords  several  new  and  curious 
compounds. 

Benzoilol  is  one  of  a  group  of  aldehyds  which  are  repre- 
sented by  the  general  formula  CWH,,_802,  and  yield  volatile 
monobasic  acids  with  04,  decomposable  into  C204  and  car- 
bohydrogens  CnHn_B,  which  form  alkaloids  CnHn_5N.  The 
essence  of  the  seeds  of  cumin  (Cuminum  cyminum)  consists 
of  such  an  ildehyd,  cuminol  C30H1203,  and  a  carbohydrogen 
homologous  with  benzen,  cymen  C20H14.  The  distillation 
of  cuminic  acid  with  baryta  affords  another  homologue,  cu- 
mcn  C1SH18.  This  with  strong  nitric  acid  yields  nitro- 
cumen,  but,  by  long  boiling  with  dilute  acid,  it  is  converted 
into  benzoio  acid  In  the  same  way  cymen  gives  rise  to  a 


458  ORGANIC   CHEMISTRY. 

new  acid,  called  lolulic  ac/t7,  which  is  C16HS04,  and  homo« 
logous  with  benzoic  and  cuminic  acids  ;  with  baryta  it  yields 
toluen  C14HS,  which  is  also  obtained  by  the  distillation  of 
tolu  balsam.  Alkaloids  homologous  with  aniline  have  been 
formed  from  all  these  hydrocarbons.  The  action  of  nitric 
acid  upon  benzen  has  failed  to  yield  an  acid  lower  in  the 
series  than  the  benzoic. 

Phenol  belongs  to  another  group  of  what  may  be  termed 
alcohols,  which  are  represented  by  the  general  formula 
CnHH_602.  There  is  still  another  class  of  aldehyds,  repre- 
sented by  CnHn_s04,  which  are  consequently  metameric  with 
the  acids  of  the  benzoic  group,  and  which  form  acid  with  06. 
Such  is  salicylol,  the  essential  oil  of  Spirea  ulmaria,  (queen 
of  the  meadow.) 

SALICYLOL,  C14H604. 

794.  This  is  obtained  by  distilling  the  flowers  of  spirea 
with  water ;  the  oil  does  not  pre-exist  in  the  plant,  but  is 
formed  during  the  process,  like  benzoilol,  by  the  reaction  of 
principles  in  the  plant  which  have  not  yet  been  examined. 
It  may  also  be  formed  fromsah'cme,  a  vegetable  principle  ex- 
tracted from  several  species  of  Salix,  to  which  both  substances 
owe  their  name.    Salicylol  is  a  colorless  liquid,  heavier  than 
water,  in  which  it  is  somewhat  soluble,  and  has  the  fragrant 
odor  which  is  perceived  when  the  flowers  of  spirea  are  bruised. 
Its   composition  CJ4II604  is  identical  with  that  of  benzoic 
acid.     One  atom  of  hydrogen  in  it  may  be  replaced  by 
chlorine  or  bromine,  and  an  atom  of  hydrogen  is  also  re- 
placeable by  a  metal  yielding  compounds  like  C14H5K04. 
It  forms  a  crystalline  compound  with  ammonia,  which  soon 
changes  into  an  amid  like  hydrobenzamid. 

Heated  with  hydrate  of  potash,  hydrogen  is  evolved  and 
a  salt  of  salicylic  acid  is  formed.  The  acid  is  C14H804.  It 
crystallizes  in  delicate  white  prisms,  and  is  volatile  and 
sparingly  soluble  in  water.  Salicylic  acid  is  monobasic, 
a/id  has  considerable  resemblance  to  the  benzoic ;  it  forms 
a  coupled  acid  with  nitric  acid. 

795.  The  ethers  of  salicylic  acid  are  easily  formed  :  that 
of  methol  is  interesting,  because  it  constitutes  the  principal 
part  of  the  fragrant  essential  oil  of  winter-green,  Gaultheria 
t>rocumbenSj  obtained  by  distilling  that  plant  with  water. 

The  ether  is  readily  decomposed  by  an  alcoholic  solution 


ESSENTIAL  OILS. 

of  hydrate  of  potash,  and  yields  wood-spirit  and  salicylato 
of  potash.  If  to  the  hot  solution  of  the  salt  an  excess  of 
chlorohydric  acid  is  added,  the  salicylic  acid  crystallizes  on 
cooling.  Ammonia  converts  the  ether  into  a  crystalline 
mass  of  salicylamid,  which  has  the  composition  of  salicylate 
of  ammonia  minus  H203. 

When  the  salicylic  acid  is  rapidly  distilled,  it  is  decomposed 
into  carbonic  acid  and  phenol  C14H604  — C204-f  C13H603. 
If  strong  nitric  acid  is  added  to  the  oil  of  winter-green  or 
salicylic  acid,  and  the  mixture  boiled  so  long  as  red  vapors 
appear,  a  large  quantity  of  trinitric  phenol,  nitropicric  acid, 
is  obtained  on  cooling. 

The  essences  of  anise,  fennel,  and  some  other  plants,  con- 
sist principally  of  an  oil,  to  which  the  name  of  anethol  has 
been  given.  It  is  C^H^Oa :  by  oxydizing  agents,  such  as 
nitric  acid,  it  is  converted  into  oxalic  acid,  and  a  new  acid 
resembling  the  salicylic  and  homologous  with  it,  which  is 
called  anisic  acid  C16H806.  Its  decomposition  yields  car- 
bonic acid  and  anisol  C14H802,  a  homologue  of  phenol. 

OTHER  ESSENTIAL  OILS. 

796.  The   essences  just  described  are  types  of  a  large 
Dumber  of  essential  oils,  which,  although  not  all  homologous 
with  the  classes  named,  sustain  the  relation  of  aldehyds  or 
alcohols  to  corresponding  acids.     Such  is  the  oil  of  cinna- 
mon, which  is  G1SHS03,  and  yields  by  oxydation  cinnamic 
acid  C1SH804.     This  acid  is  associated  with  the  benzoic, 
which  it  resembles,  in  its  properties,  in  the  balsam  of  tolu : 
by  nitric  acid  it  is  oxydized  and  yields  benzoic  acid.    When 
distilled  with  baryta  it  is  decomposed  into  carbonic  acid  and 
a  carbohydrogen,  cinnamen  C16H8. 

Both  cinnamol  and  cinnamen  appear  to  exist  in  the  bal- 
sams, such  as  styraXj  benzoin,  tolu,  and  the  balsam  of  Peru. 
These  consist  of  resinous  matters,  apparently  formed  by  the 
oxydation  of  essential  oils,  and  mixed  with  cinnamic  or 
benzoic  acids,  or  with  both. 

797.  The  oxygenized  essences  already  described  are,  as  in 
the  case  of  cuminal,  often  associated  with  other  oils,  which, 
like  cymen,  contain  no  oxygen,  and  these  carbohydrogen  oils 
sometimes  constitute  the  only  product  of  the  distillation. 
The  most  important  of  this  class  has  the  formula  G80H8, 
and  is  best  known  under  the  form  of  oil  of  turpentine.     It 
is  obtained  by  distillation  from  the  crude  turpentine  which 


460  ORGANIC    CIIEMISTR*. 

exudes  from  many  species  of  PI'HUH,  and  is  a  mixture  of  the 
volatile  oil  and  a  resin.  Its  taste  and  odor  are  well  known ; 
it  has  a  specific  gravity  of  -8(35,  and  boils  at  312°.  It  is 
insoluble  in  water,  but  soluble  in  alcohol.  Oil  of  turpentine 
is  of  great  use  in  the  arts,  for  the  preparation  of  varnishea 
and  paints,  and  is  used  for  illumination,  under  the  names  of 
camphcne  and  pine-oil.  The  liquids  sold  for  the  same  pur- 
pose, under  the  names  of  burning-fluid  and  Kpirit-yas,  are 
solutions  of  camphene  in  highly  rectified  alcohol,  and,  from 
their  great  volatility  and  inflammability,  are  very  liable  to 
explosion  and  dangerous  accidents. 

798.  The  oils  of  juniper,  pepper,  caraway,  parsley,  citron, 
lemon,  oranye,  and  bcryamot  are  carbohydrogens,  identical  in 
composition,  density,  and  boiling  point  with  oil  of  turpentine, 
and  may  be  included  under  the  general  name  of  camphen. 
They  absorb  chlorohydric  acid  gas,  and  yield  a  crystalline 
compound,  which  is  C2JI10.IIC1  — C20H17C1,  and  has  all  the 
characters  of  a  substitution  product  from  020II18.    The  liquid 
portion  of  the  oil  which  has  been  treated  with  the  gas  has 
the  same  composition   as  the    solid.      This  is  crystalline 
and  volatile,  and  has  an  odor  like  ordinary  camphor.     The 
essence  of  citron,  unlike  the  others,  fixes  2HC1,  and  yields 
a  compound  C20II18Cla.    These  chlorinizcd  bodies  are  decom- 
posed when  distilled  with  lime,  arid  yield  modifications  of 
camphen,  distinguishable    principally  by  their    odors   and 
their  different  action  upon  polarized  light. 

799.  When  moist  oil  of  turpentine  is  exposed  to  cold,  it 
often  deposits  a  crystalline  compound :  a  similar  substance 
is  slowly  separated  from  a  mixture  of  the  oil  with  alcohol 
and  nitric  acid.     It  crystallizes  in  beautiful  prisms,  and  is 
volatile,  very  soluble  in  alcohol,  and  sparingly  soluble  in 
water.     The  composition  of  this  new  body  is  represented 
by  C/20H20O4,  and  it  is  therefore  formed  by  the  fixation  of 
2EIa03;    it  crystallizes  with    an    additional  equivalent  of 
water,  which  is  expelled  by  heat :   the  name  of  terebol  is 
given  to  it.     When  dissolved  by  boiling,  in  water  acidulated 
with  sulphuric  or  chlorohydric  acid,  it  is  completely  decom- 
posed  into  water  and  a  volatile  liquid,  terpinol,  which  is 
obtained  by  distillation  and  has  an  odor  of  hyacinths  :  it  is 
C40H.14Oa.     Chlorohydric  acid  gas  expels  water  from  fused 
tcrol/ol,  and  yields  Ofl0H18Clfl,  a  crystalline  body  identical  iu 
composition  with  that  obtained  from  lemon  camphen. 

The  odors  of  these  different  varieties  of  the  same  carbo 


ESSENTIAL  OILS.  461 

hydrogen  depend  upon  differences  in  constitution  not  yet 
understood;  they  are  apparently  independent  of  the  pre- 
sence of  any  oxygenized  compound,  as  the  different  essences 
may  be  distilled  from  hydrate  of  potash  or  potassium,  with 
no  other  effect  than  that  of  refining  their  odors.  The  oil  of 
roses  is  a  carbohydrogen  of  different  composition,  probably 

(AjQlljjjy 

800.  Many  of  the  oxygenated  volatile  oils  deposit,  by 
cold,  crystalline  compounds  which  are  often  isorneric  with 
the  oils  themselves,  and  are  distinguished  by  the  general 
name  of  stcaroptcns,  or  camphors  of  their  respective  oils,  from 
their  resemblance  to  common  camphor.     This  substance  is 
obtained  by  distilling  the  wood  of  the  Lauras  camphora  with 
water,  and  is  crystalline,  very  volatile,  fragrant,  and  soluble 
in  alcohol,  but  insoluble  in  water.    Its  formula  is  CaoHlfl03; 
heated  with  hydrate  of  potash  under  pressure,  it  combines 
directly  with    it   and   forms  a  salt,  campholate   of  potash 
Cao(H17K)04.     With  strong  nitric  acid  it  yields  camphoric 
acid  C30Hlfl08,  which  is  bibasic. 

801.  The  Drybalanops  camphora  of  Borneo  yields  a  solid 
fragrant  essence,  which  is  known  as  Borneo  camphor,  and  is 
much  valued  in  the  East:  it  also  exists  in  the  essential  oil  of 
valerian.    This  camphor  has  the  formula  C20FI1803,  and,  when 
heated  with  nitric  acid,  loses  Ha  and  yields  laurel  camphor. 
When  distilled  with  anhydrous  phosphoric  acid,  it  yields  a 
form  of  camphen  which   exists  with  the  camphor  in   the 
plant,  and  fixes  HaOa  to  form  it.     When  laurel  camphor  is 
thus  distilled,  a  carbohydrogen  Ofl0H14  is  obtained,  which  is 
ci/men. 

802.  The  essential  oil  of  black  mustard-seed  Sinapia  niyra, 
is  obtained  by  distilling  the  bruised  seeds  with  water.     It 
is  heavier  than  water,   pungent   and  acrid,   and  contains 
sulphur.     It  is  represented  by  the  formula  C8H5NSa.    With 
ammonia  it  combines  and  forms  a  crystalline  alkaloid,  thioxi- 
namine,  C3H8NaS2,  which,  when  heated  with  oxyd  of  lead, 
loses  H3Sa  and  forms  sulphuret  of  lead  and  water,  together 
with  a  new  alkaloid  C9H0N9,  called  sinamine,  which  is  crys- 
talline, and  is  a  strong  base. 

The  essential  oil  of  horse-radish,  Oochlcaria,  ojjlcinaluj  is 
identical  with  that  of  mustard.     The  oil  of  asafootida  con 
tains  carbon,  hydrogen,  and  sulphur:  it  is  probably  C19H13S$, 
and  seems  allied  to  a  sulphuretted  ether  or  alcohol :  with 
chlorid  of  mercury  it  forms  a  crystalline  compound  which 


462  ORGANIC   CHEMISTRY. 

contains  the  elements  of  the  oil  with  those  of  the  mercurial 
salt.  When  mixed  with  sulphocyanid  of  potassium,  a 
decomposition  ensues  which  gives  rise  to  the  essential  oil  of 
mustard.  The  oil  of  garlic  belongs  to  the  same  series,  which 
is  very  interesting  from  its  curious  and  as  yet  imperfectly 
known  relations. 

The  odorous  secretion  of  the  polecat,  Mephitis  putorius, 
contains  sulphur,  and  perhaps  belongs  to  the  same  class. 

803.  Resins. — These  substances  are  vegetable  products, 
and  seem  to  have  been  generally  formed  by  the  oxydation 
of  essential  oils ;  they  are  insoluble  in  water,  but  soluble  in 
alcohol  and  ether,  and  many  of  them  are  used  in  pharmacy 
and  in  the  arts.     Among  them  are  copal)  mastic,  clemi, 
guiacum,  and  colophony  or  pine  resin.     In  their  crude  state 
they  are  often  mixed  with  volatile  oils,  which  may  be  sepa- 
rated by  distillation  with  water,  as  those  of  turpentine  and 
elemi,  or  with  soluble  acids,  like  the  benzoic  and  cinnamic, 
as  in  the  balsams,  and  often  with  gums  and  other  principles 
soluble  in  water,  constituting  what  are  called  in  the  materia 
medica,  yum  resins,   like  asafoetida  and    gamboge.      The 
true  resins  are  many  of  them  acids,  and  form  distinct  salts 
with  bases.     The  resin  of  the  pine  may  be  obtained  by  care- 
ful management  from  its  alcoholic  solution,  in  crystalline 
crusts,  very  soluble  in  ether  and  sparingly  soluble  in  alcohol. 
Exposed  to  heat,  it  distils  over  and  condenses  in  an  isomeric 
modification,  distinguished    in  its  crystallization  and  solu- 
bility.     Under  certain  circumstances,  both  varieties  may 
be  converted  into  an  amorphous  form.     They  have  been 
denominated  pimaric  and  sylvic  acids,  and  are  both  mono- 
basic, and  represented  by  C40H3004.     Two  equivalents  of 
oil  of  turpentine  and  06,  yield  H30a  and  an  equivalent  of 
pimaric  acid.      The  resins  of  copaiva,  elemi,  and  anime  be- 
long to  one  or  another  of  the  modifications  of  this  acid. 

804.  Caoutchouc,  Gum-Elastic. — This  curious  substance  in 
found  in  the  juices  of  many  plants,  but  is  principally  obtained 
from  the  Hcvea  guianesis,  and  latropha  elastica.     Its  ordi- 
nary properties  are  well  known  :  it  is  insoluble  in  water  and 
alcohol,  but  dissolves  in  ether  and  many  volatile  hydrocar- 
bons :  when  softened  by  these  solvents,  it  is  wrought  into 
a  great  variety  of  curious  and  useful  articles.     Small  tubes 
of  gum-elastic  are   very  useful  in  the  laboratory,  to  join 
glass  tubes  and  form  flexible  joints.     They  are  easily  made 
from  sheet  caoutchouc  by  cutting  the  folded  edges  of  the 


VEGETAL   ACIDS.  463 

with  clean 
scissors  over  a  glass 
tube,  as  seen  in 
figure  417.  Caout- 
chouc is  very  com- 
bustible, and  burns 
with  a  bright  smoky 
flame.  It  contains  Fig.  417. 

carbon  and  hydrogen  only,  and  probably  in  equal  equivalents; 
but  it  furnishes  no  reactions  by  which  we  may  fix  its  formula  or 
even  determine  whether  it  is  chemically  homogeneous.  When 
exposed  to  heat  it  is  decomposed,  and  yields  several  volatile 
hydrocarbons  homologous  with  olefiant  gas  :  among  them 
are  said  to  be  CSH8,  C10H10,  and  C40H40.  These  mixed 
liquids  are  used  as  a  solvent  for  caoutchouc }  the  volatile 
oils  from  coal4ar  are  also  employed  for  the  same  purpose. 
When  caoutchouc  is  immersed  in  a  bath  of  melted  sulphur, 
or  when  sulphur  is  added  to  its  substance  and  the  mate- 
rial afterward  exposed  to  a  considerable  heat,  (280°,)  the 
caoutchouc  undergoes  a  peculiar  change.  It  becomes  much 
firmer  and  stronger,  and  less  liable  to  be  softened  by  heat  or 
rendered  rigid  by  cold;  in  this  form  it  is  known  as  vulcanized 
gum-elastic,  and  is  extensively  used  in  the  arts,  in  preference 
to  the  unaltered  caoutchouc.  This  is  Goodyear' s  patent. 

805.  Gutta  Percha. — This   substance   exudes   from   the 
Isonandra  gutta,  a  tree  common  in  the  Malaccan  peninsula, 
and  forms  a  tough  and  elastic  mass  at  ordinary  temperatures, 
which  becomes  ductile  and  plastic  when  warmed  by  immer- 
sion in  hot  water.     Gutta  percha  (pronounced  pertcha)  is 
a  mixture  of  several  resins,  which  are  separable  from  each 
other  by  means  of  their  different  solubility  in  alcohol  and 
ether.     The  greater  portion  of  it  consists  of  a  resin  which 
softens  at  104°  F.,  and  is  but  little  soluble  in  cold  ether 
when  pure.     It  contains  a  greater  amount  of  oxygen  than 
pimaric  acid.     Gutta  percha  is  readily  dissolved  by  chloro- 
form and  sulphuret  of  carbon,  which  deposit  it  unchanged 
by  evaporation.     It  is  capable  of  being  moulded  into  a  great 
many  articles  of  utility  and  ornament. 

VEGETAL  ACIDS. 

806.  Besides  the  acids  which  we  have  described  as  derived 
from  bodies  of  the  alcohol  group,  or  from  the  various  essen- 
tial oils,  and  which  are  generally  monobasic,  volatile,  and. 


164  ORGANIC   CHEMISTRY. 

when  of  high  equivalents,  sparingly  soluble  in  water,  there 
remains  to  be  described  a  class  of  acids  of  high  equivalents, 
which  are  bibasic  or  tribasic,  very  soluble  in  water,  and 
contain  a  large  amount  of  oxygen,  having  analogies  with  the 
lactic  acid.  Such  are  the  oxalic,  citric,  tartaric,  and  malic 
acids,  and  some  others  of  less  consequence. 

807  Oxalic  Add,  C4H208.—  The  salts  of  this  acid  exist 
in  many  vegetables  :  the  agreeably  sour  taste  of  the  wood- 
Borrel,  Oxalis  acetosella,  of  the  common  sorrel,  a  species  of 
RumeXj  and  many  other  plants,  is  due  to  the  acid  oxalate  of 
potash  which  they  contain,  and  from  which  the  acid  may  be 
extracted.  It  is  also  a  product  of  the  action  of  nitric  acid 
upon  alcohol,  upon  sugar,  starch,  lignin,  and  many  other 
organic  substances.  To  prepare  it,  one  part  of  sugar  is  heated 
with  eight  parts  of  nitric  acid,  specific  gravity  1-25.  A 
violent  action  ensues,  and  much  nitrous  acid  is  evolved; 
when  this  ceases,  the  solution  is  concentrated  by  evaporation, 
and  on  cooling  yields  a  large  quantity  of  crystals  of  oxalic 
acid,  which  are  purified  by  washing  in  a  little  cold  water 
and  recrystallization. 

808.  Oxalic  acid  forms  colorless*  crystals,  which  are 
C4H208-f-2Ha02;  by  a  gentle  heat  the  water  is  expelled, 
and  the  dry  acid  remains  as  a  white  powder,  which,  at  a 
higher  temperature,  is  in  part  sublimed  unchanged,  and 
partly  decomposed  into  formic  acid,  water,  carbonic  acid 
and  carbonic  oxyd  gases.  The  acid  is  very  soluble  in  water, 
has  a  strongly  acid  taste,  and  is  poisonous.  When  the  acid 
or  one  of  its  salts  is  heated  with  strong  sulphuric  acid,  it 
is  decomposed  without  blackening,  a  character  by  which  it 
is  distinguished  from  the  succeeding  acids,  and  evolves 
equal  volumes  of  carbonic  acid  and  carbonic  oxyd  gases  j 


Oxalic  acid  is  bibasic  ;  the  neutral  oxalate  of  potash 
is  a  very  soluble  salt,  and  is  C4(K3)0S;  the  acid  oxalate 
C4(KH)08  is  less  soluble,  and  has  a  pleasant  acid  taste.  It 
is  known  under  the  name  of  bmoxatatc,  and  as  it  was  for- 
merly obtained  from  the  wood-sorrel,  is  often  sold  as  salt 
of  sorrel,  for  the  purpose  of  removing  iron-stains  from  linen, 
which  it  does  by  forming  a  soluble  salt  with  the  iron  oxyd. 
The  acid  oxalate  crystallizes  with  another  equivalent  of 
oxalic  acid  to  form  a  salt  which  is  called  a  quadroxalate, 
and  contains  C4H?Os-j-C4(HK)08,  or  one-fourth  the  amount 
of  potash  that  is  in  the  neutral  oxalate.  The  acid  might 


OXALIC   ACID.  466 

hence  be  regarded  as  quadribasic,  and  be  08H4016,  but  its 
other  reactions  lead  to  the  conclusion  that  it  is  properly 
bibasic.  The  second  equivalent  of  acid  may  be  regarded 
as  holding  a  place  analogous  to  that  of  the  crystal-water  in 
other  salts.  The  oxalate  of  ammonia  C4(NH4)308  crystal- 
lizes in  fine  prisms ;  when  decomposed  by  heat  it  loses 
2H203,  and  yields  the  amid  of  oxalic  acid,  oxamid,  which 
is  C4H4N204.  It  is  a  neutral  insoluble  body,  and  by  the 
action  of  acids  is  reconverted  into  oxalate.  The  acid  oxa- 
late of  ammonia  yields  in  like  manner  an  acid  amid,  oxa- 
mic  add,  C^IA+^HS^^H.NO,  — Ha02-=C4HsN06. 
It  is  monobasic,  and  forms  a  series  of  salts  :  when  its  solution 
is  boiled  it  is  changed  into  acid  oxalate  of  ammonia. 

The  oxalate  o.f  lime  crystallizes  with  2H303;  it  is  a  very 
insoluble  salt,  and  occupies  an  important  part 
in  the  vegetable  economy,  being  secreted  by 
a  large  number  of  plants,  in  the  cells  of  which 
the   microscope  reveals  a  great  number   of 
beautiful   crystals    of  this   substance ;    this 
appearance  is  represented  in  figure  418,  of  a 
vessel  from   the   bark  of  Torreya  taxifolia. 
In  many  of  the  lichens,  the  oxalate  of  lime 
appears  to  replace  the  woody  fibre,  and  to  be        Fig-  418. 
somewhat  allied  in  its  functions  to  the  carbonates  and  phos- 
phates of  lime  in  the  animal  kingdom.     The  oxalates  of  the 
inctals  are  generally  insoluble. 

With  two  equivalents  of  the  alcohols,  oxalic  acid  forms 
neutral  ethers ;  and  with  one,  vinic  acids.  The  oxalic  ether 
of  wood-spirit  is  obtained  in  fine  crystals ;  it  is  C4(Me2)Os : 
mixed  ethers  of  tlie  different  alcohols  may  be  obtained,  such 
as  C4(EtMe)08.  When  ammonia  in  excess  is  added  to 
oxalic  ether,  oxamid  is  obtained ;  but  if  the  ammonia  is 
cautiously  added,  a  beautiful  crystalline  substance  is  formed, 
which  is  named  oxamethane,  and  regenerates  an  oxalate, 
alcohol  and  ammonia,  by  fixing  2Ha02.  It  corresponds  to 
sulphamethane,  and  is  at  once  the  amid  of  oxalovinic  acid, 
and  the  ether  of  oxamic  acid.  Oxalic  acid  pertains  to  the 
series  already  described  under  oleic  acid,  including  succinic 
and  suberic  acids,  and  represented  by  C»H,*_208 ;  when  fused 
with  hydrate  of  potash  it  yields  a  formate. 

809.  Tartaric  Acid,  C8.H8013. — This  acid  exists  in  the 
juices  of  many  fruits,,  particularly  that  of  the  grape,  as  an  acid 
fcartrate  of  potash.  As  this  salt  is  almost  insoluble  in  dilute 

£Xi 


466  ORGANIC   CHEMISTRY. 

alcohol,  it  is  deposited,  during  the  fermentation  of  wine,  in 
crystalline  crusts,  known  as  crude  tartar,  or  anjol.  It  is 
decomposed  by  chalk  to  form  a  tartrate  of  lime ;  this  is 
mixed  with  an  equivalent  of  sulphuric  acid,  which  forms  a 
sulphate,  and  liberates  the  tartaric  acid.  From  a  concen- 
trated solution  it  crystallizes  in  fine  rhombic  prisms,  very 
soluble  in  water  and  alcohol,  and  having  a  pleasant  acid 
taste.  Tartaric  acid  is  bibasic.  The  acid  tartrate  of  potash 
CS(H5K)013  is  prepared  by  refining  the  crude  tartar  by 
crystallization,  and  generally  appears  as  a  crystalline  powder, 
sparingly  soluble  in  water,  and  feebly  acid  to  the  taste.  It 
is  known  in  pharmacy  as  cream  of  tartar.  The  neutral 
tartrate  is  mu«  h  more  soluble  in  water,  and  is  commonly 
called  soluble  tartar.  It  is  Cs(H4Ka)013.  By  saturating 
cream  of  tartar  with  carbonate  of  soda,  a  double  salt  is  ob- 
tained which  is  Cs(H4KNa)013 :  it  forms  very  large  transpa- 
rent prismatic  crystals,  and  is  known  as  Rochelle  salt. 

810.  When  cream  of  tartar  and  oxyd  of  antimony  are 
boiled  together  in  water,  solution  takes  place,  and,  on  cool- 
ing, transparent  crystals  of  a  double  salt  are  deposited,  which 
is  known  in  medicine  by  the  name  of  tartar  emetic. 

The  part  which  the  oxyd  of  antimony  plays  in  this  com- 
pound is  peculiar.  We  may  represent  two  equivalents  of 
oxyd  of  antimony  2Sb03  =  Sb306  as  (SbOa)303,  correspond- 
ing to  H303,  and  the  group  SbOa  will  then  be  equivalent  to 
H,  and  may  replace  it  in  combination.  The  salt  in  ques- 
tion is  such  a  compound,  and  the  acid  tartrate  being 
C8H4(HK)013,  tartar  emetic  dried  at  212°  is  C8H4(Sb09.K) 
O13.  The  crystals  at  the  ordinary  temperature  contain  H30a 
as  water  of  crystallization,  but  lose  it  by  a  gentle  heat.  If 
the  dried  salt  is  heated  to  428°,  it  breaks  up  into  water 
HaOa,  and  a  salt  which  is  C8Ha(SbK)Oia  :  in  this  compound 
antimony  in  one-third  its  ordinary  equivalent  may  be  sup- 
posed to  replace  hydrogen  as  in  the  analogous  compounds  of 
the  sesqui-oxyds  :  if  we  call  this  Sbj,  stibicum,  and  repre- 
sent it  by  sb,  the  dried  salt  then  becomes  C8Hfl(sb.K)Oia : 
it  is  then,  however,  quadribasic.  Oxyd  of  uranium  UOS 
may  in  the  same  way  replace  H  in  a  tartrate,  and  by  heat 
Uj,  corresponding  to  sb,  and  represented  by  ur  may  be 
obtained  in  combination,  replacing  H  :  in  this  way  all  the 
hydrogen  is  removed  and  a  compound  obtained  which  is 
C8(urasb3)0ia.  Arsenious  acid  As03  and  boracic  acid  BoOa 


VEGETAL  ACIDS.  467 

rifford,  with  bitartrate  of  potash,  compounds  analogous  to 
these  salts  of  oxyd  of  antimony. 

Tartaric  acid  dissolves  peroxyd  of  iron  and  forms  a  very 
soluble  salt :  in  this,  as  in  the  preceding  compounds,  the 
metal  is  not  precipitated  by  solutions  of  potash  or  ammonia. 
The  decomposition  of  tartaric  acid  by  heat  produces  several 
new  acids,  which  have  not  yet  been  thoroughly  studied. 

811.  The  crude  tartar  obtained    from   the  wine  of  the 
Vosges  some  years  since,  was  found  to  contain  an  isomerio 
modification  of  tartaric  acid,  which  is  less  soluble  than  the 
ordinary  acid,  and  crystallizes  with  an  equivalent  of  water, 
while  the  common  form  is  anhydrous  :  the  new  acid  precipi- 
tates solution  of  the  salts  of  lime,  and  in  the  chemical  cha- 
racters of  several  of  its  salts  is  distinguished  from  the  ordi- 
nary tartaric  acid,  with  which  however  it  is  metameric  :  it 
has  received  the  name  of  racemic  acid.     The  replacements 
of  the  crystals  of  tartaric  acid  and  of  its  salts  are  upon  alter- 
nate angles,  constituting  what  is  called  a  hemihedral  modi- 
fication, and  the  order  of  the  replacements  is  from  left  to 
right  :  a  solution  of  tartaric  acid  or  of  any  tartrate  acts 
upon   polarized   light,  and  causes  the  ray  to  rotate  in  the 
same  direction.     Racemic  acid  and  its  salts  are  not  hemi- 
hedral, and  do  not  affect  in  any  way  the  ray  of  polarized 
light.     When,  however,  a  solution  of  the  double  racemate  of 
potash  and  ammonia  is  crystallized,  two  sets  of  crystals  are 
obtained  in  equal  quantities :  the  one  are  hemihedric  to  the 
right,  and  identical  in  all  respects  with  the  ordinary  tartrate 
of  these  bases  :  the  others  have  left-handed  hemihedrism,  and 
cause  the  beam  of  polarized  light  to  deviate  to  the  left ;  and 
these  two  salts  contain  two  tartaric  acids  which  are  distinguish- 
ed from  each  other  only  by  their  opposite  hemihedral  modi- 
fications and  their  action  upon  polarized  light.     The  right- 
handed  acid  is  ordinary  tartaric  acid,  and  the  left-handed  a 
new  and  a  distinct  modification  ;  and  these  two  are  not  by 
any  known  means  convertible  into  one  another.     The  forma 
of  the  two  crystals  are  to  each  other  as  the  image  in  a  mirror 
is  to  the  object.     When  saturated  solutions  of  the  two  acids 
are  mixed,  they  become  warm,  and  deposit  crystals  of  the 
racemic  acid,  in  which  their  mutual  influence  upon  polarized 
light  is  neutralized. 

812.  Malic  Acid,  CSH,.010. — This  acid  exists  in  the  juices 
of  many  sour  fruits,  particularly  in  the  apple  and  the  ber- 
ries of  the  mountain  ash,  Sorlus  aucuparia :  the  stems  of 


4GS  ORGANIC    CIIEMTST11V. 

the  garden  rhubarb  also  contain  a  large  quantity  of  it  tt 
is  very  soluble  in  water  and  alcohol,  and  crystallizes  with 
difficulty  ;  its  solution  has  a  pleasant  sour  taste.  The  malic 
acid  is  bibasic,  and  the  malates  of  the  alkaline  bases  are 
very  soluble.  The  acid  malate  of  ammonia  CS(H.NH4)010 
forms  large  transparent  crystals.  The  neutral  rnalate  of 
lead  C8(H4Pb2)010  is  obtained  as  a  white  readily  fusible 
precipitate,  which  in  an  acid  liquid  slowly  changes  into 
delicate  crystals.  Malic  acid  is  not  volatile,  but  is  decom- 
posed by  heat  into  water  and  new  acids,  which  are  described 
in  the  larger  works. 

813.  When  tartaric  and  malic  acids  are  heated  with  anhy- 
drous alcohol,  vinic  acids  are  obtained  corresponding  to  the 
sulphovinic.     The  neutral  ethers  are  more  difficult  of  prepa- 
ration, as  they  are  soluble  in  water  and  not  volatile  :  by 
passing  hydrochloric  acid  gas,  however,  through  the  alco- 
holic solutions  of  the  acids,  neutralizing  the  excess  of  acid 
with  carbonate   of  soda,  and  agitating   the  mixture  with 
hydric  ether,  the  ethers  of  the  acids  are  dissolved  out,  and 
may  be  obtained  by  evaporating  the  solution  at  a  gentle 
heat.     They  are    converted  by  ammonia  into   amids  and 
ethers  of  amidic  acids  :  in  this  way  tartramic  acid  and  tar- 
tramid  may  be  obtained. 

814.  Malic  ether  yields  malamid,  which  has  the  compo- 
sition of  and  appears  to  be  identical  with  asparagine,  a 
peculiar  nitrogenized  principle  found  in  the  juices  of  the 
asparagus,  mallows,  and  particularly  in  the  young  shoots  of 
vetches  which  have  vegetated  in  the  dark.     It  forms  large 
crystals,    sparingly   soluble   in    cold    water,    and    contains 
C8H8N306,  corresponding  to  malate  of  ammonia  from  which 
the  elements  of  water  have  been  abstracted,  CSH4(NH4)3010 
— 2H302  =  C8H8NaO?:  by  the  action  of  alkalies  or  acids  i* 
loses  ammonia  and  yields  aspartic  acid  C8H7N08,  which  is 
now  found  to  be  identical  with  tnalamic  acid,  and  to  be 
formed  from  acid  malate  of  ammonia  as  oxarnic  acid  is  from 
the  acid  oxalate. 

The  ordinary  action  of  acids  or  alkalies  does  not  further 
decompose  this  acid ;  but  when  nitric  oxyd  is  passed  into  a 
solution  of  asparagine  or  aspartic  acid  in  nitric  acid,  the 
hyponitrous  acid  formed,  decomposes  the  aspartic,  yielding 
malic  acid,  nitrogen,  and  water,  by  a  decomposition  similar 
to  that  described  under  aniline :  CSH  N08+NH04=  C8Ha01Q 


VEGETAL   ACIDS.  4G9 

Citric  Acid,  C13H8014. — This  acid  exists  in  the  juices  of 
many  fruits,  often  associated  with  the  tartaric  and  malic, 
and  is  the  acid  of  lemons.  It  is  obtained  by  saturating 
lemon-juice  with  chalk,  by  which  an  insoluble  citrate  of 
lime  is  formed ;  this  is  decomposed  with  an  equivalent  of 
sulphuric  acid,  which  forms  sulphate  of  lime,  and  the  citric 
acid  is  obtained  by  evaporation  and  crystallization.  It  forms 
large  crystals  belonging  to  the  trimetric  system ;  it  is  very 
soluble  in  water,  and  has  a  strong  but  agreeable  acid  taste. 
The  citric  acid  is  tribasic,  and  forms  with  potash  three  salts, 
in  which  one,  two  and  three  atoms  of  hydrogen  are  replaced 
by  potassium  :  the  first  two  salts  are  acid,  and  the  last,  which 
is  C13(H5K3)014,  is  neutral.  In  the  same  way  it  yields  a 
neutral  ether  with  three  equivalents  of  alcohol,  and  vinic 
acids  with  one  and  two  equivalents. 

When  exposed  to  heat,  citric  acid  is  decomposed  into 
H202  and  C12H6013 ;  this  is  a  new  acid,  which  is  also  found 
combined  with  lime  in  the  Aconitum  napellus,  and  is  hence 
called  aconitic  acid ;  it  is  tribasic  and  very  soluble  in  water: 
when  the  action  of  heat  is  carried  still  further,  the  acoui- 
tic  acid  is  decomposed  into  C304  and  C10H00S;  this  last  ia 
called  citraconic  acid,  and  is  bibasic,  soluble,  and  by  heat 
distils  in  part  unchanged  :  a  higher  temperature  decomposes 
it  into  water,  and  a  neutral  liquid  CaoH406.  This  sub- 
stance, which  is  called  citraconid,  slowly  dissolves  in  water, 
and  combines  with  Ha03  to  form  an  acid  isomeric  with  citra- 
conic acid. 

815.  Tannic  Acid,  Tannin. — Many  plants  contain  a 
peculiar  principle,  characterized  by  an  astringent  taste,  and 
by  precipitating  animal  gelatine  from  its  solutions,  forming 
with  it  an  insoluble  compound,  upon  the  production  of  which 
depends  the  prosess  of  tanning  leather.  The  barks  of  oak 
and  hemlock,  and  gall-nuts,  which  are  excrescences  resulting 
from  the  puncture'  of  insects  upon  the  branches  of  a  species 
of  oak,  contain  a  large  portion  of  this  principle,  which  ia 
named  tannic  acid,  and  are  used  in  the  preparation  of 
leather :  they  are  also  employed  with  persalts  of  iron  in 
dyeing  black,  and  in  the  formation  of  writing-ink.  The 
vegetable  extracts  called  kino  and  catechu,  and  many  other 
vegetable  substances,  contain  a  principle  analogous  to  the 
tannin  of  the  oak.  Tannic  acid  is  obtained  in  a  pure  state 
from  gall-nuts,  which  yield  about  one-third  of  their  weight, 
by  the  following  process: — They  are  reduced  to  a  coarse  pow- 


470  ORGANIC   CHEMISTRY. 

der,  and  placed  in  the  upper  part  of  a  vessel  like  that  repre- 
sented in  the  figure,  the  mouth  of  which  is 
previously  stopped  with  a  piece  of  linen,  and  a 
quantity  of  hydric  ether  is  then  poured  over  them, 
which  slowly  filters  through,  and  collects  in 
the  lower  vessel,  where  it  separates  into  two 
layers.  Ordinary  ether  contains  about  one- 
twelfth  of  water,  which  dissolves  the  tannic  acid 
to  the  exclusion  of  all  other  substances,  and 
forms  a  solution  that  does  not  mix  with  the  ether, 
which  dissolves  a  portion  of  coloring  matter  from 
the  gall-nut.  The  dense  aqueous  solution  is 
separated,  washed  with  a  little  ether,  and  finally 
evaporated  in  shallow  vessels  by  a  gentle  heat. 
It  forms  a  brilliant  porous  mass,  which  has  gene- 
rally a  light  yellow  tint;  it  is  very  soluble  in 
water  and  has  a  purely  astringent  taste.  Sul- 
jjj  phuric,  nitric,  chlorohydric  and  phosphoric  acids 
give  copious  precipitates  with  its  solution,  which 
ng.  419.  are  combinations  of  the  two  acids.  The  tannic 
is  a  feeble  acid,  and  is  bibasic  or  polybasic.  The  alkaline  tan- 
nates  are  soluble ;  those  of  the  metals  are  generally  insoluble, 
and  often  colored.  The  pertannate  of  iron  is  the  basis  of 
black  dyes;  and  of  writing-ink  :  it  is  insoluble  in  water,  but 
when  the  solutions  are  dilute,  the  precipitate  remains  a  long 
time  suspended,  especially  if  a  little  gum  is  added,  as  in 
the  fabrication  of  ink.  When  a  solution  of  tannic  acid  in 
potash  is  heated,  a  salt  of  gallic  acid  is  formed,  with  the 
production  of  a  brown  matter.  Similar  results  are  obtained 
when  strong  acids  act  upon  tannin,  and  the  powder  of  nut- 
galls  mixed  with  water  undergoes  a  sort  of  fermentation, 
which  also  yields  gallic  acid.  When  boiled  for  some  time 
with  dilute  sulphuric  acid,  tannin  is  converted  into  gallic 
acid  and  grape  sugar.  The  brown  products  obtained  with 
strong  acids  and  alkalies,  result  from  the  decomposition  of 
the  sugar  which  is  produced.  The  probable  formula  of 
tannic  acid  is  C52H24032;  two  equivalents  of  it  with  6H302 
yield  one  of  glucose,  C^H^O^,  and  two  of  gallic  acid, 

Gallic  Acid,  C14H6010. — This  acid  exists  ready  formed 
in  the  seeds  of  the  mango  :  it  is  most  easily  prepared  by 
the  process  of  fermentation  already  described ;  it  is  dissolved 
out.  of  the  mixture  by  boiling  water,  and  separates  on  cool- 


VEGETAL   ALKALOIDS.  471 

ing  in  small  silky  crystals,  which  require  100  parts  of  cold 
water  for  their  solution,  and  have  an  acid  and  astringent 
taste.  Gallic  acid  does  not  precipitate  gelatine,  and  the 
black  color  of  the  pergallate  of  iron  is  destroyed  by  boil- 
ing. Gallic  acid  is  bibasic :  its  salts  have  been  but  little 
studied.  When  carefully  heated,  it  is  decomposed  into  Ca04 
and  a  crystalline  sublimate,  which  is  pyrogallic  acid,  and  is 
C13H600.  It  is  very  soluble  in  water  and  alcohol,  and  when 
dissolved  in  a  solution  of  hydrate  of  potash,  absorbs  oxygen 
so  rapidly  from  the  air  as  to  be  employed  in  eudiometry. 

Both  gallic  and  pyrogallic  acids  reduce  the  salts  of  plati- 
num, gold,  and  silver.  An  application  of  this  is  made  for 
the  purpose  of  coloring  the  human  hair,  which  is  first  wet 
with  a  solution  of  gallic  acid,  and  then,  after  drying,  moist- 
ened with  an  ammoniacal  solution  of  a  salt  of  silver.  The 
reduced  metal  imparts  a  fine  black  or  brown  color  to  the 
hair,  which  is  permanent. 

For  a  large  number  of  other  vegetable  acids,  many  of 
which  are  yet  but  imperfectly  known,  the  student  is  refer- 
red to  more  extended  treatises. 


VEGETAL  ALKALOIDS. 

816.  The  artificial  organic  alkaloids  which  we  have  de- 
scribed under  different  heads  in  the  preceding  pages,  have 
been  considered  as  derivatives  of  ammonia  in  which  one  or 
more  atoms  of  hydrogen  are  replaced  by  the  elements  of 
some  carburet  of  hydrogen  j  such  are  aniline  and  metha- 
mine.  We  have  pointed  out  how  these,  like  ammonia,  may 
fix  the  elements  of  water,  and  form  compounds  analogous 
to  hydrate  of  potash,  such  as  the  hydroxyd  of  vinic  ammo- 
nium (NEt4.H)03 ;  but  when  these  combine  with  an  acid, 
the  oxygen  is  eliminated  in  the  equivalent  of  water  which  is 
formed,  and  it  is  but  the  group  NEt4,  which  replaces  hydro- 
gen in  the  acid.  There  are,  however,  a  large  number  of 
organic  bases  occurring  in  different  vegetable  substances, 
which,  like  aniline  and  ammonia,  combine  directly  with  acids 
without  the  formation  of  water,  and  which  contain  oxygen. 
All  of  these  alkaloids  contain  one  and  sometimes  two  atoms 
of  nitrogen,  and  may  be  regarded  as  derivatives  of  ammonia 
in  which  the  group  of  elements  replacing  hydrogen  contains 
oxygen.  They  are  commonly  crystalline  and  not  volatile 


472  ORGANIC    CHEMISTRY. 

without  decomposition,  and  generally  possess  active  medi* 
cinal  powers.  Those  of  opium,  cinchona,  hellebore,  and 
many  others  constitute  the  active  principles  of  these  drugs. 
When  exposed  to  heat,  especially  in  the  presence  of  caus- 
tic alkalies,  they  are  decomposed,  and  generally  evolve 
volatile  alkaloids  without  oxygen  ;  among  these,  methamine 
and  aniline  are  met  with.  Several  other  volatile  alkaloids 
obtained  by  the  action  of  a  solution  of  hydrate  of  potash 
upon  plants,  are  supposed  to  be  the  result  of  a  similar 
decomposition. 

817.  Many  of  the  vegetal  alkaloids  are  strong  bases,  and 
completely  neutralize  acids ;  others  are  comparatively  feeble, 
and  their  salts  are  even  decomposed  by  a  gentle  heat. 

They  combine  with  chlorid  of  platinum  to  form  double 
salts,  which  are  generally  sparingly  soluble,  and  analogous 
to  the  chlorid  of  platinum  and  ammonium  :  some  of  them 
unite  with  one,  and  others  with  two  equivalents  of  the  chlo- 
rid, and  in  like  manner  they  frequently  form  two  chloro- 
hydrates  by  fixing  one  and  two  equivalents  of  chlorohydric 
acid,  thus  giving  rise  to  neutral  and  acid  salts.  The 
alkaloids  combine  with  metallic  salts  in  the  same  way  as 
ammonia,  and  yield  compounds  with  nitric  acid,  and  with 
nitrate  of  silver.  They  generally  form  combinations  with 
chlorid  of  mercury,  which  have  a  similar  composition  with 
the  ammonia  salts.  We  shall  first  describe  some  of  the 
more  important  of  the  oxygenized  alkaloids,  and  then  pro- 
ceed to  speak  of  those  amilogous  to  aniline. 

818.  Alkaloids  of  Cinchona,  or  Peruvian  Bark. — The 
barks  of  several  species  of  cinchona  owe   their  medicinal 
properties  to  the  presence  of  two  alkaloids,  which  are  named 
quinine  and  cinckonme.     They  are  extracted  by  digesting 
the  bark  in  a  dilute  acid,  and  adding  to  the  infusion  a  solution 
of  carbonate  of  soda,  which  precipitates  the  alkaloids  in  an 
impure  state.     The  precipitate  is  washed 'and  dissolved  in 
boiling  alcohol ;  a  little  animal  charcoal  is  added  to  remove 
some  coloring   matter,  and  the  filtered  liquid,  on  cooling, 
deposits   crystals  of    cinchonine,   while   the    more    soluble 
quinine  is  obtained  by  evaporation.  Quinine  is  a  white  crys- 
talline substance,  sparingly  soluble  in  water,  but  readily  so 
in  alcohol  and  ether. 

The  formula  of  this  alkaloid  is  CSSH33N204.  It  is  readily 
soluble  in  acids,  forming  crystallizable  safts;  which  have  a  very 


VEGETAL   ALKALOIDS.  473 

bitter  taste.  These  are  two  chlorohydrates,  one  C38H33N304 
HC1,  which  if  we  would  compare  it  with  chlorid  of  ammo- 
nia, must  be  written  (C3SH23N304)C1  =  QuCl,  and  a  second 
acid  salt  QuOl.HCl,  or  C3SH33N304.2HC1 ;  the  platinum 
double  salt  corresponds  to  this  acid  chlorohydrate :  there 
exists,  in  like  manner,  two  sulphates  of  quinine,  which  with 
several  other  salts  of  this  base  are  employed  in  medicine. 
Cinchonine  is  represented  by  C33H22N303;  it  differs  from 
quinine  only  by  03,  and  resembles  that  base  in  its  charac- 
ters, but  is  less  soluble  in  alcohol  and  ether.  Its  salts  are 
similar  to  those  of  quinine,  and  are  often  substituted  for  the 
latter  in  medical  practice. 

819.  In  the  preparation  of  these  alkaloids,  a  portion  of 
quinine  is  often  obtained  as  an  uncrystallizable  resinous 
mass,  which  is,  however,  identical  in  chemical  composition 
and  medicinal  properties  with  the  crystalline  base.  It  is 
called  quinoidine.  The  cinchona  known  in  commerce  as  pale 
bark  contains  principally  cinchonine;  the  yellow  bark  qui- 
nine, and  the  red  bark,  a  mixture  of  both.  Different  varie- 
ties of  cinchona  have  furnished  two  or  three  other  bases  very 
similar  to  these;  to  which  the  names  of  aricine,  chinova- 
tine,  and  quinidine  have  been  given. 

These  bases  are  accompanied  with  a  peculiar  acid,  called 
quinic  or  kinic  acid  ;  it  forms  large  crystals  resembling  tar- 
taric  acid,  and  is  bi basic :  its  composition  is  represented  by 
C14H13012.  The  results  of  its  decomposition  form  a  very 
interesting  series. 

By  the  action  of  chlorine  and  bromine  upon  solutions  of 
chlorohydrate  of  cinchonine  the  hydrogen  of  the  alkaloid 
is  in  part  replaced,  and  blchloric  and  bibromic  cinchonine  are 
obtained ;  the  former  is  C3gH30ClaNa03,  and  is  isomorphous 
with  the  normal  alkaloid. 

When  cinchonine  is  distilled  with  hydrate  of  potash,  a 
carbonate  is  formed  and  hydrogen  gas  escapes,  with  a  new 
volatile  base  named'  chinoline  or  qninolt'ne,  which  is  an  oily 
liquid  and  resembles  aniline  in  its  properties.  Its  compo- 
sition is  represented  by  C18H7N :  C35H33N302-f-2(KH)03  = 
2C18H7N-f-CaK300-f  5Hfl.  Quinine  and  strychnine  yield 
chinoline  by  a  similar  process. 

Alkaloids  of  Opium. — This  substance  is  the  inspissated 
juice  of  the  capsules  of  a  species  of  poppy,  Papaver  somni- 
ferum,  and  contains  several  organic  bases.  The  most  im- 
portant of  these,  and  the  one  to  which  it  owes  its  power  aa 


474  ORGANIC   CHEMISTRY. 

an  anodyne,  is  morphine.  It  is  prepared  by  precipitating 
a  solution  of  op:'im  by  carbonate  of  soda,  as  in  the  process 
for  quinine  ;  the  impure  morphine  is  digested  in  cold  alcohol 
to  remove  some  other  alkaloids  present,  and  finally  dissolved 
in  dilute  acetic  acid.  The  cautious  addition  of  ammonia  to 
the  acetate  thus  formed,  precipitates  the  morphine,  which 
is  dissolved  in  hot  alcohol,  and  crystallizes  on  cooling.  It 
forms  brilliant  rectangular  prisms,  which  are  sparingly  soluble 
in  water,  readily  so  in  hot  alcohol,  and  insoluble  in  ether; 
it  has  a  persistent  bitter  taste.  Its  formula  is  C34H19N06. 
Morphine  forms  crystalline  salts,  some  of  which,  as  the 
chlorohydrate,  sulphate,  and  acetate,  are  employed  in  medi- 
cine. The  best  opium  contains  six  or  eight  per  cent,  of  this 
alkaloid. 

820.  Codeine  is  a  base  which  occurs  in  small  quantities 
with  morphine ;  it  is  more  soluble  in  water  than  that  alka- 
loid, and  dissolves  readily  in  ether :  it  seems  allied  to  mor- 
phine in  its  effects  upon  the  animal  system.  The  formula 
for  codeine  is  C3GH31N08.  When  heated  with  sulphuric  acid, 
codeine  yields  a  compound  which  is  derived  from  the  sulphate 
by  the  elimination  of  2H302,  and  corresponds  to  an  amid: 
morphine  and  some  other  alkaloids  yield  similar  compounds. 
Bases  have  been  obtained  from  it  in  which  portions  of  the 
hydrogen  are  replaced  by  chlorine,  bromine,  and  the  nitric 
elements.  When  heated  with  potash  it  evolves  volatile 
bases,  among  which  are  ammonia  and  methamine. 

Nareotine  is  another  alkaloid,  which  occurs  in  consider- 
able quantity  in  opium,  and  is  separated  from  the  morphine 
by  being  very  soluble  in  ether  and  insoluble  in  water.  It 
forms  brilliant  transparent  crystals,  and  has  the  formula 
C^HjggNO,^  Nareotine  is  but  a  feeble  base  :  by  oxydizing 
agents  it  is  decomposed,  and  yields  a  peculiar  acid  called 
the  opianic  C20H10010,  and  a  new  alkaloid,  cotarnine 
C26H13N08.  In  addition  to  these  there  have  been  observed 
several  other  bases  in  smaller  quantities  in  opium :  such 
are  narceine,  papaverine,  and  theuaine ;  they  are  but  little 
known.  Opium  contains  also  a  peculiar  tribasic  acid,  the 
meconic  C14H4014.  It  is  not  improbable  that  in  certain 
seasons  and  conditions  of  soil  and  climate,  different  alkaloids 
may  be  formed  in  the  same  plant,  and  to  an  extent  replace 
each  other ;  that  such  is  the  case  with  different  species  of 
a  genus  is  shown  by  the  history  of  cinchona  and  some  other 
pjants. 


VEGETAL   ALKALOIDS.  475 

821.  Strychnine. — This  alkaloid  is  found  in  the  StryJinoa 
fiux-vomica,  and  several  other  plants  of  the  same  genus.    It 
is  prepared  by  digesting  the  nux-vomica  with  water  acidu- 
lated by  sulphuric  acid,  and  precipitating  the  solution  by 
caustic  lime.     The  impure  precipitate  is  boiled  with  alcohol 
and  animal  charcoal,  and  the  liquid  on  cooling  deposits  the 
strychnine  in  crystals.     It  is  almost  insoluble  in  water,  abso- 
lute alcohol,  and  ether,  but  dissolves  in  dilute  alcohol :  its 
salts  are  crystallizable,  intensely  bitter,  and  highly  poisonous. 
Strychnine  and  its  compounds  produce  a  spasmodic  affection 
of  ,the  muscles  of  voluntary  motion;  they  are  used  in  minute 
doses  in  cases  of  paralysis.     The  poison  of  the  celebrated 
upas  is  the  product  of  the   Stryclmos  tieute,  and  owes  its 
activity   to   strychnine.       The   formula   for   strychnine   is 

C«HMNa04; 

Brucme  is  another  organic  base,  which  is  associated  with 

the  last,  in  several  species  of  StrycJinos.  It  resembles  strych- 
nine but  is  more  soluble  in  water  and  alcohol,  and  although 
similar  in  its  action  upon  the  animal  system,  is  less  potent. 
Its  formula  is  C46H20N208.  Both  of  these  bases  yield  pro- 
ducts in  which  the  hydrogen  is  in  part  replaced  by  chlorine 
and  bromine. 

822.  Pipermeis  a  crystalline  alkaloid  extracted  from  black 
pepper,  and  is  a  feeble  base :  the  formula  C70H36N3010  is 
assigned  to  it.     When  heated  with  a  mixture  of  hydrate  of 
potash  and  quick-lime  it  disengages  two  volatile  bases,  one 
of  which  appears  to  be  picoline,  an  alkaloid  which  is  meta- 
meric  with  aniline,  and  is  obtained  as  a  product  of  the  dis- 
tillation of  bones.     The  other,  to  which  the  name  of  piperi- 
dine  is  given,  has  the  formula  C10H±1N  :  it  boils  at  212°  F., 
is  soluble  in  water,  caustic,  and  has  a  strong  odor  of  am- 
monia.   Piperidine  is  homologous  with  arsine  and  stibethine, 
having  the  general  formula  CJH^^N;  N  being  replaceable 
by  As  or  Sb.     These  are  alcoholic  ammonias  which  have 
lost  H2,  and  may  have  one,  two,  or  three  atoms  of  the  hydro- 
gen in  NH3  replaced  by  the  alcoholic  elements.     Thus  arsine 
has  but  one,  and  stibethine  three  equivalents  of  the  carbo- 
hydrogen,  while  the  new  base  has  two,  which  may  corre- 
spond  to  the   vinic  and  propionic,  C4  and  C6;  or  to  the 
butyric  and  methylic,   C8  and  C3.      Piperdine,   with   one 
equivalent  of   hydriodic   ether,  exchanges  H  for  C4H5,   to 
form  a  new  base ;  but  with  a  second  yields  an  iodid,  which 


476  ORGANIC    CHEMISTRY 

isNC10H10Et2.I,  and  corresponds  to  the  iodid  of  vinic  am- 
monium. 

823.  Theme;  Caffeine,  C16H10N404.—  This  organic  base  is 
found  in  coffee,  tea,  the  fruit  of  the  Paullnia  sorbalis,  and 
the  Ilex  paraguayensis,  which  affords  the  matte,  or  Paraguay 
tea.  It  is  most  abundant  in  green  tea,  which  contains  from 
two  to  five  per  cent.  ;  the  best  coffee  does  not  yield  one  per 
cent.  To  obtain  it,  a  strong  decoction  of  tea  is  mixed  with 
a  solution  of  the  surbasic  acetate  of  lead,  as  long  as  a  pre- 
cipitate is  formed;  to  the  clear  solution  a  little  ammonia  is 
added  to  precipitate  the  excess  of  lead,  and  the  liquid  by 
evaporation  furnishes  theine  in  delicate  silky  crystals.  It 
is  readily  soluble  in  hot  water  and  alcohol,  and  may  be 
volatilized  without  decomposition  ;  its  taste  is  slightly  bitter, 
Theine  is  a  feeble  base,  and  its  salts*  are  easily  decomposed  . 
the  chlorohydrate  crystallizes  beautifully.  With  nitrate  of 
silver  it  yields  a  salt  in  fine  crystalline  groups,  which  is 


It  is  worthy  of  notice,  that  the  plants  which  furnish  this 
alkaloid  are  used  by  different  nations  to  prepare  a  grateful 
and  gently  stimulating  beverage.  As  these  substances 
resemble  each  other  only  in  containing  theine,  it  is  probable 
that  they  owe  their  common  properties  to  the  presence  of 
this  principle,  and  that,  in  some  unknown  manner,  it  pro- 
motes digestion  and  the  other  vital  functions.  The  Bra- 
zilians prepare  from  the  fruit  of  the  Pauluiia  sorbalis  an 
extract  called  by  them  yuurana,  which  is  much  esteemed 
as  a  remedy  in  dysentery  and  nephritic  complaints;  it  con- 
tains a  considerable  quantity  of  tbeine. 

824.  The  seeds  of  the  2  hcobroma  cacao,  from  which  cho- 
colate is  prepared,  yield  an  alkaloid  thcobrominc,  which  re- 
sembles caffeine  and  is  homologous  with  it  :  it  is  C14HSN404, 
and  the  common  formula  of  the  two  is  therefore  CnHn_6. 
•N404.  With  chlorine  and  oxydizing  agents  these  alkaloids 
yield  a  series  of  interesting  bodies,  to  which  we  shall  again 
advert. 

825.  Sola-nine,  from  the  Solanum  nigrum,B.Did  several  other 
species,  —  hyoscyamine,  from  Hyoscyamus  niyer,  —  atropine, 
from  Atropa  belladonna,  and  daturine,  from  Datura  stramo- 
nium, are  alkaline  principles  which  possess  in  great  perfection 
the  poisonous  properties  of  the  plants  from  which  they  are 
derived.  They  are  obtained  by  somewhat  complicated  pro- 
cesses, and  are  crystalline  and  volatile.  Their  salts  are 


VEGETAL   ALKALOIDS.  477 

employed  in  medicine.  Veratrine  is  found  in  the  Veratrum 
album,  or  white  hellebore;  it  forms  a  white  crystalline 
powder,  which  is  insoluble  in  water,  but  soluble  in  alcohol. 
It  is  a  powerful  acrid  poison,  but  is  used  medicinally  in 
neuralgia  with  beneficial  results.  Aconitine  is  obtained 
from  the  Aconitum  napettus,  and  resembles  veratrine  in  its 
properties.  Sanguinarine  is  an  alkaloid  which  exists  in  the 
blood-root,  Sanguinaria  canadensis,  and  to  which  this  plant 
owes  its  active  properties.  Emetine,  the  emetic  principle 
of  ipecacuanha,  is  also  an  organic  alkaloid.  There  are  many 
other  oxygenized  bases  which  have  been  artificially  formed. 
Such  are  benzoline,  which  has  been  described  as  an  isomeric 
modification  of  hydrobenzamid,  and  many  more,  which  the 
limits  of  this  treatise  will  not  permit  us  to  notice. 

826.  Of  the  volatile  bases  analogous  to  aniline  and  chino- 
line,  obtained  from  plants,  but  two  have  been  much  studied, 
nicotine  and  conine.     Nicotine  is  the  alkaloid  of  tobacco, 
and  is  obtained  by  distilling  a  concentrated  infusion  of  the 
plant  with  lime  or  hydrate  of  potash.     The  recent  plant 
contains  a  peculiar  crystalline  body,  called  nicotianine,  which 
affords  nicotine  by  the  action  of  caustic  potash ;  but  in  the 
prepared  tobacco,  nicotine  exists  ready  formed,  and  can  be 
extracted  by  the  action  of  ether  to  which  a  little  ammonia 
has  been  added.     When  tobacco  is  smoked  in  a  German 
pipe,  the  liquid  which  condenses  in  the  well  contains  a  large 
quantity  of  this  alkaloid.     The  strongest  Virginia  tobacco 
affords,  when  dry,  six  or  seven  per  cent,  of  the  alkaloid,  and 
mild  Havanna  tobacco  no  more  than  two  per  cent. 

The  formula  of  nicotine  is  C20H14N3.  It  is  an  oily  liquid 
heavier  than  water,  in  which  it  is  somewhat  soluble.  It 
distils  at  a  high  temperature  unchanged.  The  taste  of 
nicotine  is  very  acrid,  and  its  odor  recalls  that  of  tobacco ; 
it  is  extremely  poisonous.  This  base  is  strongly  alkaline 
and  forms  very  sojuble  salts ;  it  fixes  2HC1  to  form  a  deli- 
quescent chlorohydrate. 

827.  Conine  is  obtained  from  the  hemlock,  Conium  macu- 
latum,  by  distilling  any  part  of  the  plant  with  a  dilute 
solution  of  hydrate  of  potash.     Like  the  last,  it  is  an  oily 
liquid,  which  is  slightly  soluble  in  water,  and  possesses  in 
a  high  degree  the  smell,  taste,  and  poisonous  properties  of 
the  hemlock.     It  is  strongly  alkaline,  and  yields  a  series  of 
deliquescent  salts ;  the  formula  of  conine  is  C16H15N. 

There  still  remain  to  be  described  a  number  of  other 


478  ORGANIC   CHEMISTRY. 

vegetable  substances  which  are  not  included  under  any  of 
the  previous  classes.  Among  them  are  some  neutral  bodies, 
like  araygdaline,  salicine,  and  populine,  which  are  inte- 
resting from  the  peculiar  metamorphoses  of  which  they  are 
susceptible ;  and  besides  these,  several  substances  used  in 
coloring,  among  the  most  important  of  which,  in  regard  ta 
its  chemical  history,  is  indigo. 

828.  Amygdaline. — This  substance  exists  in  the  propor- 
tion of  four  or  five  per  cent,  in  bitter  almonds ;  it  is  also 
met  with  in  the  kernels  of  peaches  and  cherries,  and  in  the 
leaves  and  young  shoots  of  many  species  of  Sorbus,  Prunus, 
and  others  of  the  Pomacece.  It  is  obtained  from  bitter 
almonds  from  which  the  fat  oil  has  been  removed  by  pressure 
between  heated  plates,  by  boiling  the  residue  in  strong 
alcohol.  The  alcohol  is  then  distilled  off  in  a  water-bath, 
and  the  syrupy  residue,  mixed  with  a  little  yeast,  is  set  aside 
to  ferment :  by  this  treatment  a  portion  of  sugar  which  the 
almonds  contain  is  destroyed.  The  clear  liquid  is  again 
evaporated  to  a  syrup  and  mixed  with  ether,  which  precipi- 
tates the  amygdaline  in  a  crystalline  powder.  It  is  readily 
soluble  in  alcohol  and  water,  and  crystallizes  from  the  latter 
in  large  prisms,  with  three  equivalents  of  water;  it  has  a 
bitter  taste.  The  formula  of  araygdaline  is  C^H^NO^ : 
when  boiled  with  solution  of  baryta,  it  takes  up  the  elements 
of  one  equivalent  of  water,  and  is  converted  into  ammonia 
and  amygdalic  acid,  which  remains  dissolved  as  amygdalate 
of  baryta.  Amygdaline  may  be  regarded  as  the  amid  of 
this  peculiar  acid,  which  is  C^H^O^. 

Bitter  almonds  contain,  besides  amygdaline  and  a  fat  oil, 
a  large  portion  of  a  nitrogenous  substance,  to  which  the 
name  of  emulsine  is  given ;  it  constitutes  the  principal  part 
of  sweet  almonds,  which  contain  no  amygdaline.  When 
bitter  almonds  are  bruised  with  water,  or  when  an  aqueous 
solution  of  amygdaline  is  mixed  with  a  small  portion  of 
emulsine  from  sweet  almonds,  a  peculiar  decomposition 
ensues.  The  solution  acquires  the  odor  of  the  essence  of 
bitter  almonds,  and  the  amygdaline  is  found  to  be  converted 
into  prussic  acid,  benzoilol,  and  grape  sugar.  Amygdalme, 
with  two  equivalents  of  water,  contains  the  elements  of  these 
three  compounds;  C40Ha7N02a+2H202  =  C3NH+C14H6Ov 
I" ^24^34^24-  Amygdalic  acid,  when  distilled  with  sulphuric 
acid  and  peroxyd  of  manganese,  yields  also  bitter-almond 
essence,  with  carbonic  and  formic  acids.  The  action  of 


SALICINE.  479 

emulsine  in  producing  this  curious  change  may  he  compared 
to  that  of  diastase,  to  which  emulsine  has  a  certain  resem- 
blance. If  its  solution  is  heated  to  212°  F.,  it  is  precipi- 
tated in  an  insoluble  form,  and  has  no  longer  any  action  on 
amygdaline. 

829.  Salicine. — This  principle  exists  in  the  bark  of  those 
species  of  willow  which  have  a  bitter  taste.     The  decoction 
of  the  bark  is  mixed  with  the  surbasic  acetate  of  lead  as  long 
as  a  precipitate  is  formed ;  to  the  filtered  liquid  dilute  sul- 
phuric acid  is  added  to  precipitate  the  dissolved  lead,  care- 
fully avoiding  an  excess.     The  solution  is  then  decolorized 
by  animal  charcoal,  and,  by  evaporation  and  cooling,  deposits 
pure  salicine.    It  is  so  abundant  in  the  bark  of  some  willows 
as  to  separate  in  crystals  when  a  concentrated  decoction  is 
cooled.     Salicine  forms  small  white  crystals,  readily  soluble 
in  alcohol  and  water ;  it  has  a  very  bitter  taste,  and  is  em- 
ployed in  medicine  as  a  febrifuge  and  tonic.     Its  formula  is 

^52^36^38' 

When  a  solution  of  salicine  is  mixed  with  a  small  portion 
of  the  emulsine  of  sweet  almonds,  and  heated  for  some  hours 
to  105°  F.,  it  is  completely  decomposed  into  grape  sugar, 
and  a  new  compound  which  separates  in  fine  rhombohedral 
crystals,  and  is  named  saligenine.  It  contains  C14H804,  and 
its  formation  from  salicine  is  thus  represented  :  C53H3602g-f- 
2H3Oarr=C24H24024-f2C14H8Os.  Saligenine  is  readily  soluble 
in  water,  alcohol,  and  ether ;  by  the  action  of  dilute  acids 
it  loses  H203,  and  is  changed  into  a  white  substance  insoluble 
in  water,  called  saliretine.  When  a  solution  of  salicine  is 
heated  with  dilute  chlorohydric  or  sulphuric  acid,  it  is  at 
first  decomposed  into  grape  sugar  and  saligenine,  but  the 
further  action  of  the  acid  converts  the  latter  into  saliretine, 
which  separates  in  white  flakes.  When  a  solution  of  salige- 
nine is  mixed  with  chromic  acid  or  oxyd  of  silver,  these  are 
reduced,  and  the  oxygen  combining  with  the  saligenine 
forms  salicylol  and  water;  C14H804-(-Aga03=  C14H604-f 
H203-{-Ag2.  Salicine,  when  distilled  with  a  solution  of 
bichromate  of  potash  and  dilute  sulphuric  acid,  yields  a 
large  amount  of  salicylol,  identical  with  the  essence  of 
spirea  ulmaria. 

830.  Dilute  nitric  acid  by  heat  decomposes  salicine  with 
oxydation  into  grape  sugar  and  salicylol,  which,  by  oxyda- 
tion,  yields  salicylic  and  nitrosalicylic  acids;  the  final  pro- 
duct, with  a  concentrated  acid,  is  nitropicric  acid.     If  sail- 


480  ORGANIC   CHEMISTRY. 

cine  is  dissolved  in  dilute  cold  nitric  acid,  a  new  compound 
is  obtained,  which  is  formed  from  salicine  by  the  fixation  of 
oxygen  and  the  separation  of  water;  C52H3602S+04  = 
C52H34O30-j-H303.  This  substance,  which  separates  from  the 
solution  in  crystals,  is  called  lielicine,  and,  by  the  action  of 
emulsine  or  dilute  acids,  is  decomposed  into  grape  sugar  and 
salicylol,  Ca,H340M+H,0,==0MHM0!!.+2CMH,04. 

831.  Populine. — This  is  a  crystalline  substance  which  ia 
obtained  from  the  leaves  and  bark  of  the  aspen-tree,  Populus 
tremula.  It  resembles  salicine,  but  is  less  soluble,  and  has 
a  sweetish  taste.  With  acids  it  yields  benzoic  acid,  grape 
sugar  arid  saligenine,  and  when  boiled  with  a  solution  of 
baryta,  is  completely  decomposed  into  saliciue,  and  benzoic 
acid,  which  combines  with  the  baryta.  Populine  is  repre- 
sented by  CgolI^O^,  and  by  fixing  H203  is  converted  into 
salicine  and  benzoic  acid,  C80H¥08a+2H9Oa=C5aH88O?8-j- 
2C14H604.  To  indicate  this  relation,  the  name  of  bmzosalicine 
has  been  proposed  for  the  principle.  When  dissolved  in 
cold  nitric  acid,  a  new  substance  is  obtained,  which  is  termed 
benzohelicine,  and  by  boiling  with  magnesia  is  decomposed 
into  a  benzoate  and  helicine.  Neither  of  these  compounds 
is  affected  by  emulsine,  but  the  action  of  acids  and  alkalies 
converts  benzohelicine  into  grape  sugar,  and  the  mctameric 
bodies,  benzoic  acid  and  salicylol. 

832.  Phloridzine. — This  substance  is  contained  in  the  root- 
bark  of  the  apple,  pear,  cherry,  and  some  other  trees.  When 
a  concentrated  decoction  of  the  bark  is  cooled,  it  is  deposited 
in  a  crystalline  powder,  which,  when  purified,  forms  delicate 
silky  crystals,  sparingly  soluble  in  cold  water,  but  readily  in 
alcohol.  It  has  a  slightly  bitter  taste,  and  is  supposed  to 
possess  febrifuge  properties.  The  probable  formula  of  phlo- 
ridzine  is  C^H^O^,  but  it  crystallizes  with  2H20,r  When 
boiled  with  dilute  acids,  it  is  decomposed  like  salicine  into 
glucose  and  a  crystalline  insoluble  substance  called  pldorc- 
tine  C34H1308.  When  exposed  to  the  action  of  moist  air 
and  ammoniacal  vapors,  phloridzine  is  converted  into  a 
dark-blue  mass,  very  soluble  in  water,  from  which  acetic 
acid  precipitates  a  red  powder  that  dissolves  in  ammonia 
with  a  magnificent  blue  color.  It  is  called  phlorizeine, 
C4SH23024-fOs-h2NH3  ==  C48H33N3030-j-H202.  The  ammo- 
niacal solution  of  phlorizeine  is  rendered  colorless  by  proto- 
salts  of  tin,  sulphuretted  hydrogen,  and  other  deoxydizing 
agents,  but  on  exposure  to  the  air  reassumes  its  color  by 


COLORING   MATTERS.  431 

tne  absorption  of  oxygen.  This  substance  acts  the  part  of 
a  feeble  monobasic  acid,  and  gives  splendid  colored  precipi- 
tates with  metallic  salts.  If  a  salt  of  alumina  or  hydrated 
alumina  is  added  to  the  ammoniacal  solution,  it  combines 
with  all  the  coloring  matter  and  forms  a  blue  precipitate, 
leaving  the  solution  colorless. 

The  action  of  phlorizeine  with  alumina  is  analogous  to  that 
of  many  dye-stuffs,  which  form  with  oxyd  of  tin  or  alumina 
insoluble  colored  compounds.  This  property  of  alumina  has 
alrea/iy  been  alluded  to ;  when  a  tissue  of  cotton  is  first  im- 
pregnated with  a  solution  of  the  acetate  of  this  base,  then 
dried  and  immersed  in  a  hot  solution  of  a  coloring  matter 
like  phlorizeine,  this  is  precipitated,  and  the  insoluble  co- 
lored compound  is  fixed  in  the  tissue. 

833.  There  are  several  other  principles  obtained  from 
plants  or  animals,  which  are  characterized  by  this  property 
of  forming  insoluble  colored  compounds  with  metallic  oxyds, 
like  oxyd  of  tin  or  alumina,  and  are  hence  employed  in  the 
art  of  dyeing  as  coloring  matters.     We  shall  briefly  notice 
the  more  important  of  those  which  have  already  been  in- 
vestigated.   In  some  instances,  the  plants  contain  principles 
which  generate  the  coloring  matters  by  decompositions,  such 
as  we  have  seen  in  the  case  of  phloridzine.     Such  is  the 
origin  of  the  colors  of  the  lichens  and  of  madder. 

834.  Several  species  of  lichen,  as  the  Roccella  tinctoria  of 
South  America  and  the  Cape  of  Good  Hope,  the  Lecanora 
tartarea  of  Northern  Europe,  and  some  others,  are  used  for 
the  fabrication  of  a  blue  or  purple  dye-stuff,  known  by  the 
different   names  of  archil,  litmus,  cudbear,  and    tournsol. 
When  these  lichens  are  digested  in  the  cold  with  milk  of 
lime,  the  solution   yields  with  acids  a  white   precipitate, 
which  may  be  crystallized  from  alcohol  and  from  its  solu- 
tion  in  boiling  water.      It  is  an  acid,  and  forms  crystal- 
lizable  salts.     The  names  of  lecanorine,  lecanoric  acid,  and 
orscllic  acid  have  been  applied  to  it  by  different  investigators ; 
fits  composition  is  represented  by  C32H14014.     When  a  solu- 
tion of  lecanoric  acid  is  heated  to  ebullition  with  an  excess 
of  lime  or  baryta,  a  new  acid  is  formed  by  the  fixation  of 
the  elements  of  water;  C33H14014-f  H203=:2C18HS08,  which 
is  the  formula  of  the  new  acid,  to  which  the  name  of  orsel- 
linic  or  lecanorinic  has  been  given.     It  is  crystalline  and 
more  soluble  than  the  lecanoric  acid  ;  when  its  alcoholic  solu- 
tion is  treated  with  chlorohydric  acid,  or  even  when  simply 

31 


482  ORGANIC   CHEMISTRY. 

boiled,  the  crystallizable  ether  of  the  acid,  C16H7(C4H  J08  is 
obtained,  which  has  also  been  described  under  the  names  of 
pseud  erytlirine  and  lecanoric  etlicr. 

When  this  ether  is  boiled  for  some  time  with  baryta  water, 
it  is  decomposed  with  the  evolution  of  alcohol,  into  carbonic 
acid  and  a  new  substance,  orcine  ;  the  same  body  is  obtained 
by  a  similar  process  from  the  two  acids,  and  by  the  dry  dis- 
tillation of  lecanorine.  The  lecanorinic  acid  breaks  up  into 
carbonic  acid  and  orcine ;  C10H808  — C304-|-C14H804,  which 
is  the  formula  of  orcine.  It  forms  large  colorless  prismatic 
crystals  of  a  sweet  taste,  which  are  very  soluble  in  water, 
and  volatile  without  decomposition.  When  orcine  is  moist- 
ened with  ammonia  and  exposed  to  the  air,  it  absorbs  oxygen, 
and  is  converted  into  a  splendid  purple  coloring  substance, 
which  resembles  the  analogous  product  from  phloridzine, 
and  is  named  orccinc.  Its  probable  formula  is  C14H9N06 : 
orsellic  and  orsellinic  acids  also  yield  orceine  when  their 
ammouiacal  solutions  are  exposed  to  the  air. 

835.  The  lichen,  called  Ecernia  prunastri,  yields  cvernic 
acid,  which  appears  to  be  homologous  with  lecanoric  acid, 
and  to  be  C34H1(i014:  when  boiled  with  an  alkali  it  is  de- 
composed  into   orcine,  and  a  new  acid    homologous  with 
lecanorinic,  which  is  called  cverm'nic  acid  C1SH100S.     The 
Gi/rophora  2^ustulata,  known  in  Canada  as  tripe,  de  rochc, 
and  many  other  species,  contain  analogous  substances,  all 
of  which  are  available  for  the  manufacture  of  archil.     For 
this  purpose  the  lichens  are  ground  to  a  paste  with  water, 
a  solution  of  ammonia  and  sometimes  urine  is  added,  and 
the  whole  frequently  stirred,  until,  by  the  action  of  the  air} 
the  whole  of  the  orsellic  acid  is  converted  into  orceine,  when 
the  mixture  assumes  a  magnificent  purple  color.     Further 
exposure  to  the  air  turns  it  blue,  and  forms  what  is  known 
in  commerce  as  litmus.     When  the  proper  colors  have  been 
developed,  lime  and  plaster  of  Paris  are  added  to  the  mass, 
to  give  it  bulk  and  consistency,  and  the  whole  is  dried. 
Archil  is  used  with  solution  of  tin,  especially  in  the  dyeing 
of  silks.      Litmus  colors  the  common  test-paper  for  acids, 
which,  decomposing  the  blue  compound  with  lime  or  am- 
monia, set   free    the    red  orceine.     Many  salts  which  are 
capable  of  decomposing  this  feeble  combination,  restore  the 
red  color  of  litmus,  and  are  thus  said  to  possess  an  aciJ 
reaction. 

836.  The  roots  of  madder,  Rulia  tinctoria,  contain  in  theii 


COLORING   MATTERS.  48? 

recent  state,  according  to  the  latest  investigations,  a  yellow 
crystalline  substance,  called  xanthine  or  ruberythric  acidr 
which,  when  boiled  with  acids  or  alkalies,  is  decomposed  into 
glucose  and  an  orange-red  volatile  crystalline  substance, 
sparingly  soluble  in  water,  to  which  the  name  of  alizarine  is 
given.  The  formula  C30H10010  has  been  assigned  to  it.  Se- 
veral other  compounds  have  been  described  as  obtained  from 
madder,  but  alizarine  appears  to  be  the  true  coloring  prin- 
ciple. Madder  is  used  in  giving  to  cotton  the  much  valued 
Turkey-red  dye,  which  is  produced  by  the  conjoined  action 
of  a  salt  of  tin,  alumina,  and  alizarine  :  the  combination  of 
the  coloring  principle  with  alumina  forms  the  red  pigment 
called  madder  lake. 

887.  The  red  coloring  matters  of  alkanet  or  anchusa,  of 
sandal-wood,  and  of  carthamus  are  insoluble  in  water,  but 
soluble  in  alkalies,  and  appear  to  possess  acid  properties. 
The  latter,  carthamine,  is  the  coloring  principle  of  the  pink 
saucers  used  in  dyeing  flowers  and  feathers.  On  the  addi- 
tion of  acetic  acid  to  its  alkaline  solution,  it  is  precipitated 
111  an  insoluble  form,  and  then  fixes  itself  on  the  tissue 
without  the  intermedium  of  a  metallic  oxyd.  Hematoxy- 
line  is  obtained  from  logwood ;  it  is  very  soluble  and  forms 
yellow  crystals :  its  solutions  are  rendered  blue  by  alkalies 
and  red  by  acids,  and  give  a  violet  color  with  alum,  and  a 
black  with  salts  of  iron. 

The  coloring  principle  of  the  cochineal  insect  is  a  purple 
body,  very  soluble  in  water  and  alcohol ;  it  forms  beautiful 
lakes  and  scarlet  dyes  with  salts  of  tin  and  alumina,  and  has 
been  called  carminic  acid  ;  the  formula  C28H1401(5  is  assigned 
to  it.  The  pigment  known  as  carmine  is  a  lake  obtained 
from  cochineal  with  alumina. 

838.  The  yellow  coloring  matters  of  plants  are  generally 
non-azotized  substances.  Among  the  most  important  are  quer- 
citrine}  the  coloring  principle  of  the  Quercus  tinctoriat  and 
luteoline,  from  the  wood,  Reseda  luteola,  both  of  which  are 
soluble  and  crystalline.  The  yellows  of  turmeric  and  gam- 
loge  are  of  a  resinous  nature.  Others  employed  in  dyeing 
are  marine,  from  the  Morus  tinctoria,  and  annatto. 

The  leaves  of  plants  contain  a  green  resinous  matter, 
which  is  soluble  in  alcohol  and  ether,  and  seems  to  possess 
acid  properties ;  it  is  called  chlorophyll.  The  blue  and  red 
colors  of  flowers  are  very  perishable,  and  have  not  been  accu- 
rately examined.  Those  of  the  violet,  iris,  dahlia,  and  many 


484  ORGANIC   CHEMISTRY. 

other  flowers,  are  turned  red  by  acids  and  green  by  alkalies. 
A  most  delicate  test-paper  is  prepared  with  an  alcoholic  in- 
fusion of  the  petals  of  purple  dahlias. 

839.  Indiyo. — This  important  coloring  substance  is  ob- 
tained from  a  great  number  of  plants,  the  principal  of  which 
are  the  Indigofera  tinctoria  and  I.  anil,  with  some  species 
of  the  genera  Isatis,  Neriumy  and  Polygonum.     The  juices 
of  these  contain  a  peculiar  colorless  principle  in  solution, 
which,  when  exposed  to  the  air,  absorbs  oxygen,  and  is  con- 
verted into  indigo.     In  the  manufacture  of  this  substance, 
the  plants  are  steeped  in  water,  and  made  to  undergo  a  kind 
of  fermentation ;  the  clear  liquid  is  then  exposed  to  the  air, 
and  frequently  agitated  to  facilitate  the  absorption  of  oxy- 
gen j  by  this  process  it  gradually  becomes  blue,  and  deposits 
the  insoluble  indigo. 

840.  Indigo  is  obtained  in  strongly  cohering  masses  of  a 
deep  blue,  which  assume,  when  rubbed,  a  coppery  metallic 
lustre.     That  of  commerce  is  never  pure,  but  is  mixed  with 
various  foreign  matters.     Indigo  is  insoluble  in  water,  alco- 
hol, oils,  dilute  alkalies,  and  chlorohydric  acid :  when  cau- 
tiously heated  it  is  volatilized  as   a  purple  vapor,  which 
condenses  in  delicate  crystals.     The  composition  of  indigo 
is  expressed  by  C16H5N02. 

In  contact  with  water  and  de-oxydizing  agents,  indigo  is 
converted  into  a  colorless  substance,  which  is  soluble  in 
alkaline  liquids  j  this  is  generally  effected  by  a  mixture  of 
lime  and  sulphate  of  iron  :  one  part  of  indigo  in  fine  powder, 
four  parts  of  quicklime,  and  three  of  protosulphate  of  iron 
are  digested  with  a  large  quantity  of  water.  The  protoxyd 
of  iron  formed  by  the  action  of  the  lime,  reduces  the  indigo, 
which  in  this  form  is  dissolved  by  the  alkaline  solution, 
forming  a  yellow  liquid.  If  this  is  exposed  to  the  air,  oxy- 
gen is  absorbed,  and  the  indigo  is  separated  in  its  original 
color  and  insolubility.  It  is  by  impregnating  cloth  with 
this  solution,  and  precipitating  the  indigo  in  its  texture  by 
the  action  of  the  air,  that  the  fine  indigo-blue  colors  are 
produced. 

841.  Chlorohydric  acid   added  to   this   yellow  solution, 
precipitates   the  dissolved  substance  as  a  gray  crystalline 
powder,  which,  when  moist,  rapidly  becomes  blue  by  absorb- 
ing oxygen,  and  is  converted  into  indigo. 

It  is  called  indigogen,  and  has  the  formula  C33H13N304 : 
exposed  to  the  air  it  fixes  02,  and  is  converted  into  HaOa 


COLORING  MATTERS.  485 

and  2C10H5NOa.  When  indigo  is  boiled  with  an  alcoholic 
solution  of  caustic  soda  and  grape  sugar,  it  is  converted  into 
indigogen,  while  formic  acid  is  produced  by  the  oxydation 
of  the  sugar.  This  alcoholic  solution,  exposed  to  the  air, 
deposits  pure  indigo  in  crystals. 

842.  Concentrated  sulphuric  acid  dissolves  indigo  by  the 
aid  of  a  gentle  heat,  and  forms  two  acids,  (652,)  which  are 
produced  by  the  union  of  one  and  two  equivalents  of  indigo 
with  one  of  sulphuric  acid,  the  elements  of  water  being 
eliminated.     They  are  named  the  sulphindigotic  and  sulplio- 
purpuric  acids,  and,  like  their  salts,  are  intensely  blue.    The 
first  named  is  the  most  important :  when  a  solution  of  sulph- 
indigotic acid  is  boiled  with  woollen  cloth,  it  is  completely 
decolorized,  the  acid  being  taken  up  by  the  cloth ;  in  this 
way  the  color   called   Saxon  blue  is  obtained.     It  resists 
completely  the  action  of  water,  but  is  easily  dissolved  out  by 
a  solution  of  the  carbonate  of  ammonia,  which  distinguishes 
it  from  the  blue  color  obtained  with  solutions  of  indigogen. 

843.  If  powdered  indigo  is  heated  with  a  solution  of 
chromic  acid  or  dilute  nitric  acid,  it  dissolves  and  forms  a 
yellow  solution ;  this,  on  cooling,  deposits  beautiful  orange- 
red  prisms  of  a  new  substance,  called  isatine,  which  is  formed 
from  indigo  by  the  combination  of  03,  and  is  C16H5N04 : 
with  potash  it  forms  a  salt  of  isatmic  acid,  which,  when  sepa- 
rated from  the  alkaline  base,  is  decomposed  by  a  gentle  heat 
into  isatine  and  water.     Isatine  forms  several  amids  with 
ammonia.    When  it  or  indigo  is  distilled  with  caustic  potash, 
a  large  quantity  of  aniline  is  obtained  :  the  intermediate 
product  is  formed  when  indigo  is  dissolved  in  a  solution  of 
potash ;  a  yellow  solution  is   obtained,  which  appears  to 
contain  reduced  indigo,  and  a  salt  of  isatinic  acid,  but  on 
evaporating  to  dryness  and  fusing  the  mass,  hydrogen  is 
evolved,  and  carbonic  and  anthranilic  acids  are  formed.    An- 
thranilic  acid  contains  C14H7N04.    It  is  soluble,  crystalliza- 
ble,  and  volatile,  but,  when  mixed  with  sand  and  rapidly 
distilled,  is  completely  decomposed  into  carbonic  acid  gaa 
and  aniline :  C14H7N04  =  C204+913H7N. 

The  action  of  chlorine  upon  indigo  destroys  its  blue  color, 
and  transforms  it  into  a  species  of  isatine  in  which  one  and 
two  equivalents  of  hydrogen  are  replaced  by  chlorine. 
These  resemble  normal  isatine,  and,  when  distilled  with 
potash,  yield  species  of  aniline  in  which  the  same  substitu- 
tion exists.  Dilute  nitric  acid  3  inverts  indigo  by  long  boil- 


486  ORGANIC   CHEMISTRY. 

ing  into  ammonia,  carbonic,  and  nitrosalicylic  acids ;  with 
stronger  nitric  acid  it  forms  nitropicric  acid. 

THE  CYANIC  COMPOUNDS. 

844.  The  bodies  of  this  series  are  obtained  as  products 
of  a  great  number  of  reactions,  and  are  very  important  in 
their  relations  to  organic  chemtstry.     A  cyanid  was  first 
recognised  in  a  product  of  the  action  of  potash  upon  dried 
blood,  which  was  employed  for  producing,  with  a  salt  of  iron, 
a  fine  blue  pigment,  known  as   Prussian  or  Berlin  blue  : 
hence  the  name,  from  the  Greek,  kuanos,  blue. 

The  ammoniacal  salts  of  the  acids  CnHn04  yield,  as  we  have 
shown,  nitryls  by  the  loss  of  2H202,  which  regenerate  the 
ammoniacal  salt  by  again  assimilating  the  elements  of  water. 
The  general  formula  of  these  bodies  is  CnH^_jN.  The 
nitryl  of  formic  acid  ^  ^HN",  and  is  formed  when  the  vapor 
of  formate  of  ammonia  is  passed  through  a  red-hot  tube  j 
C,(H.NH4)04^C2H5N04— 2H202  ==  C2HN.  This  nitryl  is 
the  parent  of  the  cyanic  series,  and  is  commonly  known  as 
prussic  or  hydrocyanic  acid.  The  equivalent  of  hydrogen 
which  it  contains  may  be  replaced  by  a  metal,  and  the  salts 
called  cyanids  thus  obtained.  The  cyauid  of  potassium  is 
formed  when  nitrogen  gas  is  passed  over  a  mixture  of  char- 
coal and  carbonate  of  potash,  heated  to  the  temperature  at 
which  potassium  is  evolved.  It  is  sometimes  found  as  a  pro- 
duct in  furnaces  from  the  action  of  atmospheric  nitrogen 
upon  the  intensely  heated  mixture  of  carbon  and  alkali 
resulting  from  combustion  :  the  potassium  in  this  case  unites 
directly  with  carbon  and  nitrogen.  Cyanid  of  potassium  is  also 
obtained  when  animal  substances,  like  leather,  horn,  or  dried 
blood,  or  the  charcoal  obtained  from  them,  which  contains 
several  per  cent,  of  nitrogen,  are  heated  with  carbonate  of 
potash  ;  its  separation  and  purification  will  be  described 
farther  on. 

845.  Hydrocyanic  acid,  is  easily  obtained  by  distilling 
cyanid  of  potassium  with  dilute  sulphuric  acid,  or  by  decom- 
posing cyanid  of  mercury  at  a  gentle  heat  by  sulphuretted 
hydrogen ;  20JHgN+H&=2CaHN+Hg£r 

To  procure  the  anhydrous  acid,  the  best  arrangement  is 
shown  in  fig.  420.  Cyauid  of  mercury  in  coarse  powder  is 
placed  in  the  tube  a  b,  and  decomposed  by  a  gentle  cur- 
Tent  of  sulphydric  acid,  evolved  from  sulphid  of  iron  and 


CYANIC  COMPOUNDS. 


487 


diluted  sulphuric  acid.  The  sulphydric  acid  is  dried  by 
passing  it  over  chlorid  of  calcium  in  the  tube  c  d,  and  the 
product  of  the  action  is  collected  in  the  bent  tube  contained  in 
the  freezing  mixture  C.  The  operation  may  be  conducted  with- 
out danger  in  the  open  air.  Pure  hydrocyanic  acid  is  a  color- 
less limpid  liquid,  which  boils  at  80°  F.,  and  has  a  specific 
gravity  of  -697 ;  a  drop  of  it  let  fall  upon  paper,  produces  so 
much  cold  by  its  partial  evaporation,  as  to  freeze  the  remain- 
der. Hydrocyanic  acid  is  combustible,  and  burns  with  a 
white  flame;  it  is  scarcely  acid  in  its  reaction  with  test-papers : 
its  taste  is  pungent  and  aromatic,  and  its  odor  very  powerful, 
both  recall  those  of  peach  blossoms  or  bitter  almonds ;  the 
distilled  waters  of  these  substances  and  of  the  cherry-laurel, 
owe  a  part  of  their  flavor  to  the  presence  of  the  acid,  which 
is  one  of  the  products  of  the  decomposition  of  amygdaline 
by  emulsirie.  When  hydrocyanic  acid  is  mixed  with  an. 
excess  of  strong  chlorohydric  acid,  it  is  completely  decom- 
posed into  sal-ammoniac  and  formic  acid ;  boiled  with  hydrate 
of  potash,  it  is  decomposed  in  a  similar  manner,  and  yields 
ammonia  and  formate  of  potash :  C3HN-j-H203-f  (KH)Oa= 
CaHK04+NH3. 

846.  Hydrocyanic  acid  is  a  most  fatal  poison;  a  single 
drop  of  -the  concentrated  acid  placed  upon  the  tongue  of  a 
large  dog  produces  immediate  death,  and  the  diluted  acid 
even  in  very  small  doses  causes  giddiness  and  nausea.  It 
appears  to  act  as  a  sedative  to  the  arterial  system,  and  the 
suspension  of  animation  following  a  large  dose  of  it,  does  not 
always  result  in  death,  if  proper  remedies  are  employed. 
Ammonia  and  brandy  are  considered  the  most  efficient  anti- 
dotes to  its  effects.  The  vapor  of  the  acid  is  also  poisonous 
when  inhaled;  but  workmen  constantly  exposed  to  it  in  a 
diluted  state  appear  to  become  accustomed  to  it,  so  as  to 


488  ORGANIC  CHEMISTRY. 

experience  no  deleterious  effects.  The  dilute  acid  is  em« 
ployed  in  medicine  ;  when  pure,  it  readily  undergoes  sponta- 
neous decomposition,  yielding  ammonia  and  a  brown  inso 
luble  matter;  but  if  it  is  diluted,  and  a  trace  of  sulphuri* 
acid  is  present,  the  acid  may  be  preserved  for  a  long  time; 
especially  if  secluded  from  the  light. 

The  cyanid  of  potassium  CSKN  is  deliquescent  and  verj 
soluble  in  water  and  alcohol ;  it  forms  cubic  crystals,  and 
has  the  taste,  smell,  and  medicinal  properties  of  hydrocyanic 
acid:  it  is  strongly  alkaline  in  its  reactions.  Cyanid  of 
ammonium  C3AmN  =  CaH4N3  is  obtained  by  saturating  hy- 
drocyanic acid  with  ammonia,  and  is  volatile  and  very  poison- 
ous. Hydrocyanic  acid  dissolves  red  oxyd  of  mercury,  and 
the  solution  yields  colorless  crystals  of  a  cyanid  CaHgN, 
which  are  soluble  in  water  and  alcohol,  and  are  poisonous. 

Hydrocyanic  acid  and  soluble  cyanids  throw  down  from 
solutions  of  silver  a  white  curdy  precipitate  insoluble  in 
acids,  and  resembling  the  chlorid;  it  is  cyanid  of  silver,  and 
is  insoluble  in  ammonia.  Salts  of  palladium  decompose  even 
the  cyanid  of  mercury,  and  form  an  insoluble  precipitate  of 
cyanid  of  palladium.  The  other  cyanids  are  obtained  by 
double  decomposition  :  they  are  generally  insoluble  in  water, 
but  soluble  in  cyanid  of  potassium,  forming  salts,  which 
will  presently  be  described. 

The  action  of  chlorine  upon  hydrocyanic  acid  or  cyanid 
of  mercury,  yields  a  compound  in  which  chlorine  replaces 
the  hydrogen  of  the  acid  ;  it  is  a  gas  of  a  very  strong  odor, 
and  at  a  low  temperature  crystallizes  in  colorless  needles : 
it  dissolves  in  water  without  decomposition,  for  the  solution 
does  not  precipitate  salts  of  silver.  Its  formula  is  CaClN  : 
the  bromic  and  iodic  species  are  crystalline  and  very  volatile. 
These  compounds  are  commonly  called  chlorid  and  iodid 
of  cyanogen  ;  the  name  of  cyanogen  being  applied  to  the 
group  C2N,  which  plays  the  same  part  in  the  saline  combina- 
tions as  Cl  does  in  the  chlorids,  and  is  often  represented  by 
the  symbol  Cy,  the  hydrocyanic  acid  being  CyH. 

847.  When  the  carefully  dried  cyanid  of  mercury  is 
heated  nearly  to  redness,  it  is  decomposed  into  metallic  mer- 
cury, and  a  colorless  gas  which  is  liquefied  by  a  pressure  of  four 
atmospheres.  It  has  a  pungent  odor,  resembling  that  of  prussic 
acid,  and  burns  with  a  beautiful  violet  purple,  yielding  nitrogen 
and  carbonic  acid  gas;  it  is  soluble  in  water  and  alcohol,  and 
must  therefore  be  collected  over  mercury.  This  gas  is  called 


CYANIC   COMPOUNDS.  489 

cyanogen  :  the  formula  of  its  equivalent  of  four  volumes  ia 
C4N2.  It  is  therefore  not  the  hypothetical  compound  repre- 
sented by  Cy,  but  sustains  the  same  relation  to  it  that  the 
equivalent  of  four  volumes  of  chlorine,  C12  does  to  the  atom 
Cl  which  enters  into  the  composition  of  a  cblorid.  In  its 
formation,  two  equivalents  of  cyanid  of  mercury  react  upon 
each  other,  CyHg+CyHg==Hgs+Cya==C4Nfl.  When  heat- 
ed  with  potassium,  combination  ensues  with  combustion,  and 
cyanid  of  potassium  is  formed. 

Cyanogen  corresponds  to  the  nitryl  of  oxalic  acid ;  oxalate 

of  ammonia,  C4Ha08.2NHa=C4H8Na08— 4H909==C4Nr 

Its  aqueous  solution  decomposes  by  keeping,  and  a  variety  of 
products  are  obtained,  among  which  is  oxalate  of  ammonia, 
regenerated  by  a  combination  of  cyanogen  with  the  elements 
of  water.  When  one  volume  of  cyanogen  and  two  of  sulphu- 
retted hydrogen  gas  are  mixed  in  the  presence  of  water 
or  alcohol,  direct  combination  ensues,  and  the  compound 
C4Na.H4S4  is  obtained,  which  corresponds  to  sulphuretted 
oxamid :  it  forms  orange-red  crystals,  soluble  in  alcohol, 
but  sparingly  soluble  in  water.  When  boiled  with  a  dilute 
solution  of  potash,  it  evolves  ammonia,  and  is  completely 
converted  into  oxalate  and  hydrosulphate  of  potash, 
C4H4NA+4(KH)Oa=2NH8+04K808+2(KH)S8.  By 
boiling  with  chlorohydric  acid,  the  crystals  are  converted 
into  oxalic  acid,  ammonia,  and  sulphuretted  hydrogen. 

848.  Cyanates. — The  cyanids  combine  with  oxygen  to 
form  a  new  class  of  salts,  called  cyanates.  Fused  cyanid 
of  potassium  absorbs  oxygen  from  the  air,  and  reduces 
oxyd  of  copper  and  other  metals  with  ignition,  at  a  tem- 
perature below  redness.  By  adding  oxyd  of  lead,  in  small 
quantities,  so  long  as  reduction  takes  place,  the  cyanid  ia 
completely  converted  into  cyanate,  and  the  lead  separates  in 
a  metallic  state.  The  fused  mass  may  be  crystallized  by  solu- 
tion in  boiling  alcohol,  and  is  deposited  in  pearly  plates,  very 
soluble  in  water;  C2KN-f-Pb303  =  CflKNOfl-j-Pba.  Strong 
acids  liberate  the  cyanic  acid,  but  decompose  it  immediately 
into  carbonic  acid  and  ammonia.  Cyanic  acid  may  be  con- 
sidered as  the  acid  nitryl  of  carbonic  acid,  derived  from  bi- 
carbonate of  ammonia  by  the  loss  of  2Ha03.  C3H306.NH3  = 
2H3Os-{-CaHNOa.  Its  aqueous  solution  is  readily  decom- 
posed, especially  in  the  presence  of  strong  acids  and  alkalies, 
into  a  carbonate  and  ammonia,  and  the  crystals  of  cyanate  of 
potash  in  a  moist  atmosphere  attract  water,  and,  evolving 


490  ORGANIC   CHEMISTRY. 

ammonia,  are  converted  into  bicarbonate  of  potash.  Cyanic 
acid  is  obtained  in  a  pure  form  by  the  distillation  of  cyanuric 
acid :  it  is  a  colorless,  volatile  liquid,  with  an  odor  like  acetic 
acid,  and  is  very  caustic,  blistering  the  skin.  It  may  be  pre- 
served in  a  freezing  mixture,  but  at  the  ordinary  temperature 
changes  very  rapidly  into  a  white,  solid,  insoluble,  isomerio 
modification,  called  cyamdid,  which  by  heat  is  reconverted 
into  cyanic  acid. 

849.  Cyanic  acid  combines  directly  with  two  equivalents 
of  ammonia,  and  forms  a  soluble  salt  having  the  reactions 
of  a  cyanate  of  ammonia ;  but  if  its  solution  is  boiled,  am- 
monia is  evolved,  and  a  substance  having  the  composition 
of  neutral  cyanate  of  ammonia  remains  in  solution  j  it  is  an 
alkaloid,  and  combines  directly  with  acids.     The  same  com- 
pound is  obtained  as  a  product  of  the  spontaneous  decompo- 
sition of  an  aqueous  solution  of  cyanogen  or  cyanic  acid  ;  the 
ammonia  formed  from  one  portion  of  cyanic  acid,  uniting 
with  undecomposed  acid,  yields  C3HN03.NH3  =  C3H4N303. 
This  alkaloid  exists  in  human  urine,  and  has  hence  been 
named  urea.     When  fresh  urine  is  evaporated  by  a  gentle 
heat  to  a  small  bulk,  and  mixed  with  an  excess  of  nitric 
acid,  the  nitrate,  of  urea  C2H4N302.NH06,  which  is  spar- 
ingly soluble  in  the  dilute  acid,  separates  in  large  brilliant 
plates;  these  may  be  washed  with  iced  water  and  decom- 
posed with  carbonate  of  potash  :   the  urea  is  then  separated 
from   the   nitre  by  alcohol,  in  which  the  former  alone  is 
soluble. 

850.  A  better  process  for  its  formation  is  by  cyanate  of 
potash  :  the  salt  known  as  the  yellow  prussiate  of  potash  con- 
tains the  elements  of  cyan  id  of  potassium  and  cyanid  of  iron. 
It  is  dried  at  212°  F.,  and  eight  parts  of  it  are  mixed  with 
three  of  dry  carbonate  of  potash,  and  the  mixture  fused  at 
a  low  red  heat  in  an  iron  crucible :  the  iron  separates  in  a 
spongy  metallic  form,  and  a  white  crystalline  mass  is  ob- 
tained, which  is  cyanid  of  potassium,  mixed  with  about  one- 
fourth  of  cyanate,  and  is  known  in  the  arts  as  Liebig's 
cyanid  of  potassium.     If  to  this  mass,  still  in  fusion,  fifteen 
parts  of  red-lead  are  gradually  added,  the  whole  is  converted 
into  pure  cyanate  of  potash.     It  is  to  be  dissolved  in  cold 
water,  mixed  with  a  solution  of  eight  parts  of  sulphate  of 
ammonia,  and  evaporated  to  dryness.     The  cyanate  of  am- 
monia, formed  by  double  decomposition,  is  thus  converted 
into  urea,  which  is  separated  from  the  accompanying  sul- 


CYANIC   COMPOUNDS.  491 

phate  by  boiling  the  residue  in  alcohol.  It  crystallizes, 
on  cooling,  in  transparent,  colorless  prisms,  readily  soluble 
in  water  and  alcohol,  and  having  a  fresh,  sharp  taste,  like 
nitre.  It  is  a  weak  base,  but  forms  compounds  with  oxalic 
and  chlorohydric  as  well  as  with  nitric  acid ;  concentrated 
sulphuric  acid  and  hydrate  of  potash,  by  the  aid  of  heat, 
convert  it  into  carbonate  and  ammonia.  When  urea  ia 
evaporated  to  dryness  with  a  solution  of  nitrate  of  silver, 
the  elements  arrange  themselves  so  as  to  form  nitrate  of 
ammonia  and  an  insoluble  crystalline  cyanate  of  silver, 
which  explodes  by  heat.  A  solution  of  urea  heated  in  a 
sealed  tube  to  284°  F.  is  converted  into  carbonate  of  am- 
monia C2H4N304+2H303:=  C3H306.2NH3.  The  urea  in 
urine  undergoes  the  same  change  by  boiling  or  by  putre- 
faction. Nitrous  acid  at  once  decomposes  it  into  water, 
nitrogen,  and  carbonic  acid  gases,  2NH04+C2H4N2Oa  — 
3H9Oa+C204+N4. 

851.  Sulphocyanates. — Fused  cyanid  of  potassium  reduces 
sulphurets  in  the  same  way  as  oxyds,  and  combines  directly 
with  sulphur  to  form  a  cyanate  C2KNS3,  in  which  sulphur 
replaces  oxygen.  If  a  mixture  of  dried  prussiate  of  potash 
is  fused  with  sulphur  and  carbonate  of  potash  in  a  covered 
crucible,  and  the  heat  gradually  raised  to  redness,  until  the 
mass  is  in  quiet  fusion,  there  is  obtained  a  mixture  of  sulpho- 
cyanate  of  potash  and  sulphuret  of  iron.  The  salt  is  dis- 
solved out  by  boiling  water,  and  crystallizes  on  cooling. 
The  best  proportions  are  46  parts  of  the  dried  prussiate, 
17  of  dry  carbonate  of  potash,  and  32  of  sulphur.  Sulpho- 
cyanate  of  potash  forms  colorless  prismatic  crystals,  having 
a  taste  like  nitre ;  they  are  deliquescent,  and  soluble  both 
in  water  and  alcohol.  The  sulphocyanic  acid  C2HNS3  is 
obtained  in  solution  when  the  lead  salt  is  decomposed  by 
dilute  sulphuric  acid,  and  is  a  colorless  liquid  acid,  with  an 
odor  like  vinegar.  These  compounds  are  all  more  stable  than 
the  oxycyanates.  Sulphocyanate  of  ammonia  C2(NH4)NS3 
is  obtained  by  a  peculiar  reaction ;  a  solution  of  cyanid  of 
ammonium  separates  the  excess  of  sulphur  from  persulphuret 
of  ammonium,  and  if  a  mixture  of  the  two  salts  in  solution 
is  digested  with  finely  divided  sulphur,  the  sulphur  is  dis- 
solved by  the  sulphuret  and  transferred  to  the  cyanid,  which 
is  wholly  converted  into  sulphocyanate :  by  boiling  the  solu- 
tion, the  volatile  sulphuret  of  ammonium  may  then  be  ex- 
pelled, and  the  sulphocyanate  obtained  in  crystals.  Tho 


492  ORGANIC   CHEMISTRY. 

soluble  sulphocyanates  are  characterized  by  forming  a  deep 
blood-red  liquid  with  persalts  of  iron,  which  is  due  to  the 
formation  of  a  persulphocyanate  of  that  metal ;  this  reaction 
affords  a  very  delicate  test  both  for  salts  of  iron  and  sulpho- 
cyanates. 

852.  When  a  solution  of  sulphocyanate  of  potash  is  heated 
with  nitric  acid,  or  when  chlorine  is  passed  through  its  solu- 
tion, a  yellow  substance  separates,  which  contains  the  ele- 
ments of  cyanogen,  sulphur,  oxygen,  and  hydrogen,  and  has 
been  called  cyanoxsulphid ;  its  nature  is  not  well  understood. 
Exposed  to  heat,  it  yields  sulphur  and  sulphuret  of  carbon 
among  other  products,  and  leaves  a  yellow  residue  named 
mellon,  which  is  probably  C12H3ND,  and  by  a  strong  red  heat 
is  decomposed  into  cyanogen,  nitrogen,  and  hydrogen  gases. 
Mellon  decomposes  fused  sulphocyanate  of  potassa,  and  yields 
a  salt  called  mdhnid  of  potassium^  2HK3Ng.     When  this 
salt  or  mellon  is  boiled  with  a  solution  of  hydrate  of  potash, 
ammonia  is  evolved  and  a  salt  obtained,  to  which  the  name 
of  cyamellurate  of  potash  is  given;  it  isC12HK3N8Oa:  the 
corresponding  acid  is  sparingly  soluble  in  water. 

Polycyanids. 

853.  The  cyanids  exhibit  a  great  tendency  to  polymerism, 
and  form  compounds  in  which  two,  three,  and  six  molecules 
of  simple  cyanid  are  condensed  into  one.    The  mellon  series 
is  an  instance  of  such  a  polymerism.    When  cyanogen  is  ob- 
tained by  the  decomposition  of  cyanid  of  mercury,  a  portion 
of  a  black  carbon-like  body  is  always  formed,  which  is  repre- 
sented by  C13N6,  and  is  named  paracyanogen.     It  contains 
the  elements  of  three  equivalents  of  cyanogen,  and  is  entirely 
converted  into  it  when  heated  in  a  current  of  carbonic  acid 
gas;  C12Ng  — 3C4N3.     Heated  in  hydrogen   gas,   it  yields 
hydrocyanic  acid,   ammonia,   and   carbon;    C13N6 -|- H12  = 
3C3HN-|-3NH3-f-C6.     The  brown  substance  formed  by  the 
spontaneous  decomposition  of  an  aqueous  solution  of  cyano- 
gen or  of  hydrocyanic  acid,  is  similar  in  its  nature. 

854.  When  boracic  acid  or  a  borate  is  heated  with  a  cya- 
nid, a  compound  of  boron  and  nitrogen  is  obtained :  it  is,  how- 
ever, best  prepared  by  igniting  calcined  borax  with  twice  its 
weight  of  sal-ammoniac ;  the  mass  washed  with  water  and 
dilute  acids,  leaves  a  white  insoluble  powder,  which  burns 
at  a  high  temperature  with  a  green  flame,  and  when  heated 


CYANIC   COMPOUNDS.  493 

with  hydrate  of  potash  or  strong  sulphuric  acid,  is  decom- 
posed into  a  borate  and  ammonia :  the  same  decomposition 
is  produced  when  it  is  heated  in  aqueous  vapor.  It  reduces 
oxyds  of  lead,  copper,  or  mercury,  at  a  temperature  below 
redness,  with  the  evolution  of  nitric  oxyd  gas.  The  pro- 
portions of  its  elements  are  represented  by  B4N2,  but, 
from  its  fixed  nature,  it  is  probable  that  it  has  a  higher 
equivalent,  corresponding  perhaps  to  paracyanogen. 

855.  The  action  of  chlorine  upon  an  aqueous  solution  of 
hydrocyanic  acid,  the  latter  being  in  excess,  yields  a  volatile 
liquid,  which  is  C0HC12N3,  and  corresponds  to  a  triple  mole- 
cule of  cyanid  in  which  two  atoms  of  hydrogen  are  replaced. 
By  the  further  action  of  chlorine  the  third  atom  is  removed, 
and  the  perchloric  tricyanid  C6C13N3  is  obtained :   this  is 
also  formed  when  dry  chlorine  acts  upon  paracyanogen,  or 
upon  the  cyanid  of  mercury,  with  the  aid  of  sunlight,  and, 
unlike  the  monocyanid,  is  a  crystalline  solid,  which  is  vola- 
tile at  above  300°  F.     When  the  bichloric  tricyanid  above 
mentioned  is  digested  with  oxyd  of  mercury,  cyanid  of  mer- 
cury and  water  are  formed,  with  a  pungent  volatile  liquid, 
boiling  at  61°  F.,  which  is  C4C12N3,  or  &  perchloric  dicyanid, 
containing  the  elements  of  two  equivalents  of  the  mono- 
cyanid.    It  is  not  decomposed  by  water,  but  with  hydrate 
of  potash  yields  chlorid  of  potassium,  and  the  products  of 
the  decomposition  of  cyanic  acid,  ammonia,  and  a  carbonate. 

856.  The  solid  tricyanid  is  decomposed  by  water  into  chlo- 
rohydric  acid,  and  cyanuric  acid,  which  is  polymeric  of  the 
cyanic,  and  is  C6H3N306.     The  same  acid  is  formed  when  a 
solution  of  cyanate  of  potash  is  mixed  with  a  small  quantity 
of  acetic  or  nitric  acid  insufficient  for  its  complete  decompo- 
sition ;  cyanurate  of  potash  is  deposited.     When  the  com- 
pound of  chlorohydric  acid  and  urea  is  heated,  sal-ammoniac 
sublimes  and   cyanuric  acid   remains;  3C4H4N3Oa.HCl — 
3HCl.NH3-f  C6H3N306;  and  urea,  when  heated  alone  until 
it  ceases  to  evolve  ammonia,  is  converted  into  a  grayish 
mass,  which  is  an  amid  of  cyanuric  acid.    This  is  dissolved  in 
concentrated  sulphuric  acid,  the  solution  decolorized  by  a 
little   nitric  acid,  and  mixed  with  its  bulk  of  water;  the 
cyanuric  acid  separates,  on  cooling,  in  prismatic  crystals, 
feebly  acid  to  the  taste.     It  may  be  crystallized  unchanged 
from  a  boiling  solution  in  nitric  or  chlorohydric  acid,  but 
by  long  continued  ebullition  with  them,  is  slowly  decomposed 
like  cyanic  acid;  into  carbonic  acid  and  ammonia.     When 


494  ORGANIC   CHEMISTRY. 

exposed  to  a  strong  heat  it  is  decomposed  into  cyanic  acid, 
which  is  thus  obtained  pure,  C0H3N30(1==3CaHNOa. 

857.  Cyanuric  acid  is  tribasic,  and  forms  both   neutral 
and  acid  salts.     The  cyanuric  ether  of  alcohol,  obtained  by 
distilling  a  sulphovinate  with  alkaline  cyanurate  of  potash, 
forms  beautiful  crystals  sparingly  soluble  in  water,  which 
are  fusible,  volatile,  and  have  the  formula  C0(C4Ha)3Na06. 

When  sulphocyanate  of  ammonia  is  decomposed  by  heat, 
a  residue  is  obtained  consisting  of  mellon  and  an  amid  of 
cyanuric  acid,  to  which  the  name  of  melamine  is  given.  It 
is  dissolved  from  the  crude  product  by  a  dilute  boiling  solu- 
tion of  hydrate  of  potash,  and  separates,  on  cooling,  in  color- 
less rhombic  octahedrons.  It  is  C6HflN6,  and  differs  by 
3HaOa  from  the  neutral  cyanurate  of  ammonia.  Melamine 
is  a  strong  organic  base,  and  forms  crystalline  salts.  When 
boiled  with  strong  acids  or  alkalies,  it  is  slowly  decomposed 
into  ammonia  and  a  cyanurate.  The  intermediate  steps  in 
the  decomposition  are  the  amids,  corresponding  to  cyanu- 
rates  with  one  and  two  equivalents  of  ammonia,  and  are 
called  ammdid  and  ammeline.  The  latter  is  C6H5N5Oa  and 
is  a  weak  base.  By  heat  melamine  is  decomposed  into  mel- 
lon and  ammonia;  2C8H6NB=ClaH8N9-f3NH8. 

858.  Fulminates. — The  salts  which  from  their  explosive 
character  have  received  this  name,  correspond  to  the  dicya- 
nid  C4C12N2  already  described,   and  contain  the  elements 
of  two  atoms  of  cyanate.     When  nitrous  vapour  is  passed 
into  a  solution  of  nitrate  of  silver  in  alcohol,  the  fulmi- 
nate of  silver  C4AgaNa04  is  deposited.     The  same  salt  is 
formed  when  a  solution  of  silver  in  a  large  excess  of  nitric 
acid,  is  added  to  alcohol ;  the  action  is  complex;  besiies  the 
fulminate,  aldehyd,  acetic  and  formic  ethers  are  formed  by 
the  oxydizing  power  of  the  acid,  and  by  a  polyinerism  of 
the  alcoholic  molecule,  an  acid  which  is  homologous  with 
lactic  acid  and  is  C8H8013.     The  action  of  nitric  acid  upon 
alcohol  yields  aldehyd  and  nitrous  ether,  and  the  deoxyda- 
tion  of  another  portion  of  the  acid  giving  rise  to  nitrous 
acid,  this  may  react  with  the  ether  and  form  fulminic  acid 
and  water,  NH04+C4H5N04=C  JI2N304+2H2Oa.  The  sil- 
ver salt  is  sparingly  soluble  in  water,  and  forms  delicate 
white  crystals,  which  explode  with  terrible  violence  by  fric- 
tion with  any  hard  body,  even  under  water.     The  products 
of  the  decomposition  are  carbonic  acid  and  nitrogen  gases, 
and  a  mixture  of  cyanid  with  metallic  silver.  The  fulminate 


CYANIC   COMPOUNDS.  495 

of  mercury  is  less  explosive  than  the  silver  salt,  and  is  the 
material  used  in  the  preparation  of  percussion  caps.  To  pre- 
pare it,  one  ounce  of  mercury  is  dissolved  by  a  gentle  heat 
in  eight  and  a-half  ounces  by  measure  of  nitric  acid,  of  spe- 
cific gravity  1*4,  and  the  solution  is  poured  into  ten  mea- 
sured ounces  of  alcohol,  specific  gravity  '830 ;  action  soon 
ensues,  with  the  evolution  of  copious  white  fumes,  and  the 
fulminate  is  deposited  in  white  crystalline  grains,  which  are 
washed  with  cold  water,  and  dried  at  a  very  gentle  heat. 
The  salt  is  somewhat  soluble  in  boiling  water,  and  crys- 
tallizes on  cooling;  it  explodes  violently  by  a  heat  of  390° 
F.,  by  friction, 'percussion,  and  by  contact  with  strong  acids. 
Its  formula  is  C4Hg3N304.  When  fulminate  of  silver  is 
dissolved  in  nitric  acid,  one-half  of  the  silver  is  removed 
and  an  acid  salt  separates,  which  is  C4HAgN304 ;  chlorid 
of  potassium  precipitates  only  one-half  the  silver  and 
yields  C4KAgNeH4.  Metallic  copper  separates  the  whole, 
and  forms  a  copper  salt.  The  double  fulminate  of  copper 
and  ammonia  is  decomposed  by  sulphuretted  hydrogen  into 
urea,  sulphocyanic  acid,  water,  and  sulphuret  of  copper.  It 
may  be  said  to  separate  into  cyanate  of  ammonia,  which 
changes  to  urea,  and  cyanate  of  copper,  which  yields  sulphuret 
of  copper  and  cyanic  acid ;  this,  with  an  equivalent  of  H3S2, 
is  converted  into  water  and  sulphocyanic  acid. 

859.  The  relations  of  the  cyanids  to  the  bodies  of  the 
series  of  alcohols  are  full  of  interest.  When  a  sulphoviimte 
is  distilled  with  cyanid  of  potassium,  hydrocyanic  ether  is 
obtained  as  a  liquid  sparingly  soluble  in  water  and  boiling 
at  176°  F.  It  is  C3(C4H5)N  or  C6H5N,  and  is  homologous 
with  hydrocyanic  acid.  When  heated  with  hydrate  of  pot- 
ash, it  is  not  decomposed  like  other  ethers,  but  evolves 
ammonia,  and  produces  a  salt  of  propionic  acid  C6H604 
homologous  with  formic  acid.  The  hydrocyanic  ether  of 
wood-spirit  C4H3N  yields  in  the  same  way  acetic  acid, 
C4H3N+2H203r=NH3-f  C4H404.  These  ethers  are  identical 
with  the  nitryls  obtained  by  distilling  the  ammoniacal  salts 
of  these  acids  with  anhydrous  phosphoric  acid ;  the  amy- 
lic  ether  is  the  nitryl  of  caproic  acid,  C13H1304.  The  vinic 
cyanic  ether,  with  potassium,  evolves  a  gas  which  is  C4H6, 
and  the  residue  yields  to  water  cyanid  of  potassium.  A  ^ub- 
etance  remains  which  may  be  crystallized  from  boiling 
water,  and  is  an  organic  base  to  which  the  name  of  cyane- 
thine  has  been  given.  Its  formula  is  C18H15N3  corresp.ond- 


496  ORGANIC   CHEMISTRY. 

ing  to  three  atoms  of  hydrocyanic  ether,  and  it  pertains  to 
the  type  of  the  trieyanids. 

860.  When  the  crystalline  compound  of   aldehyd  and 
ammonia  is  dissolved  in  water  with  a  mixture  of  hydrocyanic 
and  chlorohydric  acids,  and  evaporated  to  dryness,  sal-am- 
moniac is  obtained,  and  the  chlorohydrate  of  a  new  base, 
which  is  formed  from   the  elements  of  aldehyd,  hydrocya- 
nic   acid  and    water,  C4H403-f  C3HN+HS02  =  C0H7N04. 
The  name  of  alanine  is  given  to  this  new  substance,  which 
is  crystalline,  soluble  in  water  and  dilute  alcohol,  and  has  a 
sweet  taste ;  an  atom  of  hydrogen  in  it  may  be  replaced  by 
a  metal,  so  that,  like  ammonia,  it  combines  both  with  acids 
and  metallic  salts.     By  the  action  of  nitrous  acid,  alanine  is 
converted  into  lactic  acid,  nitrogen  and  water,  2C6H7N04-{- 
2NH04-  C12H13012-f  2H.O.+ N4. 

861.  A  cyanic  ether  is  obtained  by  distilling  a  sulpho- 
vinate  with  cyanateof  potash;  it  is  C2(Et)NOa  =  C6H5N03, 
and  is  a  very  volatile  liquid,  which  combines  with  ammonia 
and  forms  a  body  crystallizing  in  beautiful  prisms,  and  solu- 
ble in  water  and  alcohol.     It  is  C6HSN303,  and  is  vinic 
urea,  differing  from  ordinary  urea  by  2C3H3;  when  decom- 
posed by  hydrate  of  potash,  it  yields  carbonic  acid,  and  one 
equivalent  of  ammonia,   with  one  of   ethamine,  or   vinic 
ammonia,  NEI2(C4H5).     In  the  same  way  vinic  cyanic  ether, 
which  is  homologous  with  cyanic  acid,  is  decomposed,  car- 
bonic acid  and  ethamine  being  the  only  products.  The  cyanic 
ethers  of  the  other  alcohols  yield  similar  results. 

862.  When  the  vapor  of  cyanic  acid  from  the  distilla- 
tion of  cyanuric  acid  is  passed  into  alcohol,  crystals  are 
deposited  which  contain  the  elements  of  one  equivalent  of 
alcohol  and  two  of  the  acid,  C4H603+2C2HN03:=C8HsNa06. 
This  compound  is  decomposed  by  distillation  into  alcohol  and 
cyanuric  acid,  but  with  a  solution  of  baryta,  alcohol  is  set  free 
and  the  baryta  salt  of  a  new  acid  is  formed,  which  is  called 
allophanic  arid,  and  contains  the  elements  of  two  equiva- 
lents of  a  cyanate  with  one  of  water,  being  C4H4Na00 ;  it 
differs  from  fulminicacid  by  Ha02,  and  is  monobasic.    When 
acids  are  added  to  its  salts,  or  when  a  solution  of  its  baryta 
gait  is  boiled,  it  is  decomposed  into  a  carbonate  and  urea; 
allophanic  acid  contains  the  elements  of  urea  and  carbonic 

•eld,  C4H4N206-C2H4N303+CS04- 

The  vapors  of   cyanic   acid    are  absorbed   by  aldehyd 


CYANIC   COMPOUNDS.  497 

and  a  sparingly  soluble  crystalline  compound  is  formed, 
to  which  the  name  of  irigenic  acid  is  given.  The  formula 
C9H7NS04,  representing  a  monobasic  acid,  is  assigned  to  it, 
but  its  equivalent  is  probably  more  elevated. 

863.  When  cyanogen  gas  is  passed  into  an  alcoholic 
solution  of  aniline,  sparingly  soluble  crystals  of  a  new  base 
separate.  It  has  received  the  name  of  cy aniline,  and  is 
formed  by  the  combination  of  one  equivalent  of  cyanogen 
and  two  of  aniline,  C4Na+2C18H,N  =  C28H14N4.  Its  salt* 
readily  separate  into  aniline,  and  products  of  the  decompo- 
sition of  cyanogen.  Aniline  absorbs  the  gaseous  chlorid  of 
cyanogen,  and  the  chlorohydrate  of  a  new  base  is  formed, 
C/31NJ-20uH7N  =  ClH.CJHuNa.  The  new  alkaloid  is 
called  melaniline;  it  is  crystalline,  and  its  salts  are  more 
stable  than  those  of  cyaniline.  It  combines  directly  with 
cyanogen  to  form  a  base  analogous  to  cyaniline,  to  which  the 
name  of  cyamelaniline  is  given ;  it  is  C30H13NS.  These 
bodies  are  derived  from  a  compound  of  two  equivalents  of 
aniline,  CMH14Na ;  melaniline  is  formed  from  it  by  the  sub- 
stitution of  C3N  for  H :  and  the  fixing  of  C4N2  =  (C2N)a  or 
(Jy3,  is  analogous  to  the  direct  combination  of  Cla  and  C1H. 
A  reaction  similar  to  the  last,  in  which  C2HN  or  CyH  com- 
bines directly,  is  found  in  the  vegetal  alkaloid  harmaline 
C28I!14N302 ;  when  this  base  is  mixed  with  hydrocyanic  acid 
or  its  salts  with  a  cyanid,  it  combines  with  C2HN  to  form 
a  new  crystalline  base,  cyanharmaline,  C23C14H303-}-CaHN 
=  C30H15N303.  This  combination  is  decomposed  by  heat 
into  prussic  acid  and  harmaline,  but  forms  with  acids,  salts 
which  are  permanent.  Many  other  alkaloids,  besides  ani- 
line, form  compounds  with  cyanogen  and  cyanids. 

864.  By  the  action  of  chlorine  gas  in  sunlight  upon  a 
hot  saturated  solution  of  cyanid  of  mercury,  chlorohydric 
acid,  chlorid  of  mercury,  and  sal-ammoniac  are  fonned, 
together  with  carbonic  acid,  nitrogen,  and  the  chloric 
cyanid,  which  escape  in  the  gaseous  form,  while  a  yellow 
oily  liquid  separates,  which  is  heavier  than  water,  and  has 
a  pungent  odor  and  caustic  taste.  The  formula  C13N4G114 
is  assigned  to  it;  it  is  soluble  in  alcohol  and  ether,  but  in- 
soluble in  water,  which  however  decomposes  it  into  nitro- 
gen, and  carbonic  and  chlorohydric  acids.  By  keeping, 
it  is  spontaneously  decomposed,  with  the  separation  of  per- 
chloric acetene  C4C18.  This  compound  is  probably  derived 


498  ORGANIC   CHEMISTRY. 

from  a  combination  of  six  molecules  of  cyanid,  of  which 
the  normal  species  will  be  C12H6N6,  a  group  which  is  the 
type  of  a  large  and  important  class  of  polybasic  salts,  ranch 
more  stable  than  the  ordinary  cyanids.*  The  six  atoms  of 
hydrogen  are  all  replaceable  by  a  metal,  but  two  or  three 
atoms  of  the  metallic  elements  are  combined  in  such  a  way 
as  not  to  be  recognized  by  the  ordinary  reagents,  and  like 
the  three  atoms  of  hydrogen  or  chlorine  in  the  acetic  acids, 
form  a  constant  part  of  the  acid.  The  second  atom  of  sil- 
ver in  the  fulminates,  and  the  condition  of  the  metals  in 
some  of  the  tartrates,  present  analogous  instances. 

865.  Ferrocyanids. — These  salts  may  be  represented  by 
C13(Fe2M4)N8 ;  M  being  hydrogen  or  any  metal.  The 
two  atoms  of  Fe  are  so  combined  as  not  to  be  precipitated 
by  alkalies  or  sulphurets.  The  ferrocyanid  of  potassium  is 
formed  with  the  separation  of  hydrate  of  potash,  when 
metallic  iron  or  its  oxyd  is  digested  with  a  solution  of  cyanid 
of  potassium,  hydrogen  being  evolved  in  the  former  case: 
Fe908-f  2CflKN  =  20,FeN-fK9Ofl,  which,  with  H203,  gives 
2(tiK)Oa.  The  cyanid  of  iron  unites  with  another  portion 
of  cyanid  of  potassium,  to  form  the  new  salt  C13(FeaK4)N 
This  is  the  ordinary  source  of  all  the  cyanic  compounds. 
It  is  prepared  on  a  large  scale  from  the  impure  cyanid, 
formed  by  the  calcination  of  animal  matters  with  carbonate 
of  potash,  or  by  passing  heated  atmospheric  nitrogen  over 
fragments  of  intensely  ignited  charcoal,  impregnated  with 
the  carbonate.  'In  both  processes  cyanid  of  potassium  is 
obtained,  mixed  with  excess  of  the  carbonate  of  potash.  It 
is  dissolved  in  water  and  digested  with  oxyd  of  iron,  or  a 
solution  of  protosulphate  of  iron  is  added,  until  the  precipitate 
at  first  formed  is  no  longer  dissolved  by  the  cyanid.  The 


*  Perchloric  acetene  is  decomposed  at  a  red  heat  into  Cla,  and  C4C14, 
or  perchloric  etherene.  When  this  substance  is  exposed  to  the  com- 
bined action  of  chlorine  and  water,  with  exposure  to  the  sun's  rays,  the 
compound  C^lg  is  regenerated ;  at  the  same  time,  a  portion  of  it  forma 
with  the  elements  of  water,  chlorohydric  and  chloracetic  acids;  C  Cls-f- 
2H,Oa^=3HCl^-C4Cl3H04.  We  have  seen  that  by  the  aid  of  an  amal- 
gam of  potassium,  the  chlorine  of  a  chloracetate  may  be  removed,  and 
the  normal  acetic  acid  formed.  It  has  lately  been  found  that  when  the 
vapor  of  acetic  acid  is  decomposed  at  a  red  heat,  there  are  obtained, 
besides  carbonic  acid  gas  and  acetene,  small  portions  of  benzene,  phenol, 
and  napthaline.  These  carbon  compounds,  high  in  the  organic  series, 
may  now  by  these  reactions,  be  formed,  from  charcoal,  through  the  cyanid* 


FERROCYANIDS.  499 

filtered  liquid  is  then  evaporated,  when  the  ferrocyawd  of 
potassium  separates  in  large  translucent  lemon-yellow  tabular 
crystals,  containing  3H202,  which  is  expelled  by  a  gentle 
heat.  It  is  very  soluble  in  water,  but  insoluble  in  alcohol, 
and  is  not  poisonous.  This  salt  is  known  in  the  arts  as  tho 
yellow  prussiate  of  potash,  and  is  employed  in  dyeing,  in 
the  manufacture  of  prussian  blue,  and  the  fabrication  of  the 
various  cyanids.  The  preparation  of  Liebig's  cyanid  of 
potassium,  of  the  cyanates  and  sulphocyanates,  by  means  of 
this  salt,  has  been  already  described.  When  it  is  carefully 
dried  and  fused  in  a  close  iron  vessel,  the  cyanid  of  iron  is 
decomposed  into  nitrogen  and  a  carburet,  and  pure  cyanid 
of  potassium  is  obtained,  which  may  be  crystallized  by  dis- 
solving it  in  boiling  alcohol  of  specific  gravity  -900.  When 
two  parts  of  the  dried  ferrocyanid  are  heated  with  one  of 
chlorid  of  mercury,  pure  cyanogen  gas  is  evolved,  and  by 
boiling  two  parts  of  the  crystallized  salt  with  three  of  per- 
sulphate of  mercury  and  fifteen  of  water  for  a  few  minutes, 
cyanid  of  mercury  crystallizes  on  cooling.  Distilled  with 
dilute  sulphuric  acid,  the  ferrocyanid  yields  hydrocyanic  acid, 
which  is  best  prepared  by  this  process.*  Heated  with  an 
excess  of  concentrated  sulphuric  acid,  the  ferrocyanid  under- 
goes a  peculiar  decomposition;  the  hydrocyanic  acid  evolved 
in  the  presence  of  a  strong  acid  takes  up  the  elements  of 
water  and  yields  ammonia  and  formic  acid;  but  this  last,  by 
concentrated  sulphuric  acid,  is  decomposed  into  carbonic 


*  A  dilute  acid  is  readily  prepared  by  distilling  a  mixture  of  two  parts 
of  ferrocyanid  of  potassium,  one  of  sulphuric  acid,  and  two  of  water,  and 
collecting  the  product  in  a  receiver  containing  two  parts  of  water,  until 
the  liquid  amounts  to  four  parts.  For  this  purpose  the  apparatus  shown 
in  figure  415  is  well  calculated.  This  acid,  from  the  presence  of  a  trace 
of  sulphuric  acid,  is  not  liable  to  decomposition;  it  contains  fifteen  or 
twenty  per  cent,  of  pure  acid.  To  determine  the  amount  of  real  acid 
present,  a  weighed  quantity  of  the  distilled  acid  is  added  to  a  solution 
of  nitrate  of  silver,  which  should  be  in  excess ;  the  precipitate  of  syanid 
of  silver  is  collected  on  a  filter,  dried  at  212°,  and  weighed.  Its  weight 
divided  by  5  gives  the  amount  of  real  acid  in  the  specimen.  Let  us 
euppose  that  70  grains  of  the  acid  yield  80  of  cyanid  of  silver,  equal  to 
16  of  real  acid,  70 :  16  :  :  1UO :  x,  which  equals  22-85 ;  it  then  contains 
22-85  per  cent,  of  real  acid.  But  if  it  is  required  to  reduce  it  to  any 
standard,  as  one  of  three  per  cent.,  which  is  the  ordinary  medicinal  acid, 
then  as  this  will  consist  of  97  of  water  and  3  of  real  acid,  3  :  97 : :  16  :  x, 
and  x  =  5j.7'3  grains  of  water,  which  must  be  added  to  16  of  anhydrous 
acid  to  reduce  it  to  the  standard.  But  as  70  grains  of  this  acid  contain 
already  54  of  water,  it  is  obvious  that  we  have  to  add  517'3 —  54  =  463-3 
grains  of  water  to  70  grains  of  acid  to  reduce  it  to  the  required  standard. 


500  ORGANIC   CHEMISTRY. 

oxyd  gas  and  water,  and  the  result  is  a  copious  evolution 
of  this  gas  in  a  pure  state ;  the  residue  contains  bisulphate 
of  potash,  and  a  double  sulphate  of  ammonia  and  iron. 

866.  When  a  saturated  solution  of  the  ferrocyanid  is 
mixed  with  strong  chlorohydric  acid  and  agitated  with  ether, 
a  white  crystalline  matter  separates,  being  insoluble  in  the 
ethereal  mixture;  it  is  washed  with  ether  and  dried  in  vacua, 
and  is  ferrocyanic  acid,  C12(Fe?H4)N6.     Its  taste  is  acid  and 
astringent :  it  is  very  soluble  in  water,  and  is  decomposed 
by  exposure  to  the  air,  into  hydrocyanic  acid  and  a  cyanid 
of  iron.     When  the  potash  salt  is  mixed  with  solutions  of 
salts  of  lime,  baryta,  and  zinc,  insoluble  or  sparingly  soluble 
salts  are  obtained,  which  are  CI2(FeaKCa3)N6,   &c.     The 
copper  salt  is  analogous  in  composition;  it  is  insoluble  in 
water,  and   has  an  intense  red-brown  color,  which  makes 
ferrocyanid  of  potassium  a  delicate  test  for  that  metal.    With 
a  protosalt  of  iron  a  similar  compound  is  obtained,  which 
is  greenish-white,  and  rapidly  becomes  blue  by  exposure  to 
the  air.     With  a  persalt  of  iron  a  characteristic  deep  blue 
precipitate  is  obtained,  which  is  the  pigment  prussian  blue. 
It  is  C13(Fe2fe4)N6,  the  replaceable  iron  being  in  the  form 
offerricum.    The  iron  salt  should  be  added  in  excess,  or  the 
precipitate  will  contain  a  portion  of  potassium,  like  the  pre- 
ceding compounds.      Prussian    blue  forms  a  light  porous 
mass  of  a  deep  violet-blue  color,  with  a  copper-red  reflection  : 
it  is  insoluble  in  water  and  dilute  acids,  but  when  recently 
precipitated  is  very  soluble  in  solutions  of  oxalic  acid  and 
tart-rate  of  ammonia,  forming  deep  blue  solutions  which  are 
used  as  writing-inks.     Boiled  with  a  solution  of  hydrate  of 
potash,  peroxyd  of  iron  separates,  and  ferrocyauid  of  potas- 
sium is  formed. 

867.  Ferricyanids. — When  chlorine  is  passed  into  a  dilute 
solution  of  ferrocyanid  of  potassium,  the  gas  is  absorbed,  and 
the  liquid  loses  the  power  of  precipitating  persalts  of  iron. 
On  evaporating  the  yellow  solution,  a  new  salt  is  obtained  in 
beautiful  deep  red  transparent  prisms,  which  is  known  as 
red  prussiate  of  potash  or  f&rrwyanid  of  potassium.     This 
Bait  contains  Cla(FeaK3)Nfl,  one  atom  of  K  having  been 
separated  to  form  chlorid  of  potassium  with  the  chlorine; 
but  the  iron  being  in  the  state  of  ferricum,  the  salt  becomes 
C19(fe3K3)N6,  and  the  acid  is  C12(fe3H3)N6,  and  is  tribasic. 
It  is  obtained  by  decomposing  the  lead  salt  with-  dilute  sul- 
phuric acid.     The  ferricyanid  of  potassium  does  not  affect 


NITROPRUSSIDS.  501 

the  persalts  of  iron,  but  gives  with  protosalts,  a  blue  pre- 
cipitate which  is  C13(fe3Fe3)N6 ;  it  has  a  finer  hue  than  Lhe 
ferrocyanid,  and  is  known  as  Turnbull's  blue.  When  a 
solution  of  the  red  prussiate  is  mixed  with  one  of  potash,  in 
the  presence  of  organic  matters,  ferroeyanid  is  formed,  and 
the  organic  substance  is  oxydized  by  the  oxygen  set  free. 
This  process  is  employed  in  calico-printing  for  discharging 
colors.  2C12(fe3K3)N6  =  2C12(Fe3K3)N6  +  2(KH)Oa  = 
2C13(Fe3K4)N6+H304=  H303+0a.  Peroxyd  of  hydrogen 
appears  thus  to  be  the  oxydizing  agent  in  this  reaction,  which 
is  very  energetic;  oxalates  are  converted  by  it  into  carbonates, 
and  a  solution  of  chromic  oxyd  in  potash,  into  chrornate  of 
potash.  The  same  view  may  be  extended  to  oxydation  by 
chlorine:  2Cl+2HaOa  =  2HCl+ H304. 

868.  Nitroprmsids. — "When  a  current  of  nitric  oxyd  gas 
(N03,  or  rather  N304,)  is  passed  through  a  heated  solution  of 
ferricyanic  acid,  a  reaction  ensues  which  may  be  thus  reprc- 
sented :  2C18(fe8H8)N8=2013(Fe,H8)N8+N304  =  2C9HN 
-f-2C10Fe3H3N6Os;  the  products  being  hydrocyanic  acid,  and 
a  new  substance  to  which  the  name  of  nitroprmsic  acid  has 
been  given.  When  either  the  red  or  yellow  prussiate  of 
potash  is  heated  with  nitric  acid  so  much  diluted  that  no 
nitric  oxyd  is  evolved,  nitroprussic  acid  may  be  obtained. 
For  this  purpose  844  grains  of  crystallized  yellow  prussiate 
are  pulverized,  and  mixed  in  a  capacious  vessel  with  six 
fluid-ounces  of  dilute  nitric  acid,  of  specific  gravity  1-12; 
the  heat  of  a  water-bath  is  applied  until  action  commences, 
and  is  then  removed;  the  salt  dissolves,  and  the  liquid  as- 
sumes a  dark  coffee  color,  with  a  copious  evolution  of  gas, 
consisting  of  hydrocyanic  acid  and  cyanogen,  with  some 
nitrogen,  resulting  from  a  secondary  decomposition.  When 
the  solution  is  complete,  the  heat  of  a  water-bath  is  again 
applied  until  the  liquid  gives  a  dark  green  or  slate-colored 
precipitate  with  a  protosalt  of  iron.  On  cooling,  nitrate  of 
potash  crystallizes,  and  the  liquid  is  neutralized  with  car- 
bonate of  soda,  and  boiled;  a  copious  precipitate  is  formed, 
and  the  filtered  liquid  is  of  a  clear  deep-red  color,  and  con- 
tains only  nitrates  of  potash  and  soda,  with  the  nitroprussid 
of  sodium.  The  nitrates  are  in  part  separated  by  concen- 
tration and  cooling,  and  on  evaporating  the  remaining  liquid 
at  a  gentle  heat,  the  new  salt  separates  in  ruby-red  prisms, 
resembling  in  appearance  the  red  prussiate :  its  formula  is 
C,0(Fe2Na2)N602;  the  crystals  contain,  besides,  2H202, 


502  ORGANIC   CHEMISTRY. 

The  potash  salt  is  obtained  by  substituting  carbonate  OK 
potash  for  the  soda,  but  is  more  soluble.  The  nitroprussids 
do  not  precipitate  the  persalts  of  iron,  but  yield  with  proto- 
salts  a  salmon-colored  precipitate  which  is  C10(Fe2Fea)N6Os, 
and  with  copper  salts  a  pale  green  insoluble  nitroprussid 
of  copper.  This  is  decomposed  by  a  solution  of  baryta,  and 
gives  a  soluble  baryta  salt,  which  may  be  decomposed  by 
sulphuric  acid,  and  the  nitroprussic  acid  obtained  in  dark 
*ed  crystals,  very  soluble  in  water.* 

If  a  solution  of  a  nitroprussid  is  mixed  with  one  of  an 
alkaline  sulphuret,  a  magnificent  purple  liquid  is  obtained; 
this  reaction  is  so  delicate  as  to  detect  the  smallest  trace  of 
a  soluble  sulphuret.  The  color  soon  fades  by  standing,  and 
the  solution  then  contains  ferrocyanid,  sulphocyanid,  and 
a  nitrite,  while  nitrogen,  hydrocyanic  acid,  oxyd  of  iron,  and 
sulphur  are  set  free.  Nitroprussid  of  sodium  forms  a  crys- 
talline compound  with  hydrate  of  soda  which  is  decomposed 
by  boiling;  nitrogen  gas  and  peroxyd  of  iron,  with  ferro- 
cyanid, nitrite  and  oxalate  are  the  products. 

869.  The  action  of  cyanid  of  potassium  upon  salts  of 
chromium,  manganese,  and  cobalt,  gives  rise  to  salts  which 
correspond  to  the  ferricyanids,  the  metals  being  in  the  same 
equivalent  as  in  the  sesquisalts.  The  compounds  corre- 
sponding to  ferrocyanid  have  not  been  obtained  :  when  pro- 
tocyanid  of  cobalt  is  dissolved  in  cyanid  of  potassium, 
Bcsquicyauid  of  cobalt,  cyanid  ofcdbalticum  CacoN  is  formed, 
and  potassium  is  liberated,  which,  decomposing  the  water, 
forms  hydrate  of  potash,  evolving  hydrogen  gas,  4C3CoN  + 
2CaKN=CC3coN-j-K2.  The  cobaltic  cyanid  with  another 


*  The  formula  here  given  for  the  nitroprussids  is  that  proposed  by  M. 
Gerhardt,  and  corresponds  best  with  the  original  analyses  of  the  dis- 
coverer, Dr.  Play  fair,  and  even  with  the  subsequent  results  of  Mr.  Kyd, 
whose  proposed  formula  for  the  soda  salt,  Cy§FeaNa.,NO,  is  not  admissible 
unless  it  is  doubled.  There  are  many  reasons  for  believing  that  carbon 
replaces  sulphur  and  oxygen,  somewhat  as  nitrogen  does  hydrogen,  and 
then  04Na  and  €4X3  become  equivalent  to  each  other,  while  peroxyd 
of  hydrogen  H,,04  and  nitrous  acid  NH04  correspond  to  cyanic  acid, 
NII(C202),  and  hydrocyanic  acid  C2IIN,  to  C2H«y  and  to  water  OaH3. 
The  nitroprussids  are  then  ferrocyanida  which  have  lost  IIj,  becoming 
bibasic,  and  under  the  influence  of  04N2  have  exchanged  Cy=C2N  for 
its  equivalent  02N.  The  formula  will  then  be  written  (Cy5.OiN)FeaNaa 
=  (^loOzXFe^NaJXg.  A  similar  view  may  be  extended  to  a  great  number 
of  compounds  ;  nitrobenzene,  for  example,  is  benzoilol  in  which  N  replaces 
H  and  Oa  replaces  C2;  thus,  (C13Oa)(HiN)Oa,  corresponding  to  CuH6Oa. 


ACIDS  OF  THE  URINE  AND  BILE.  503 

portion  of  cyanid  of  potassium  forms  the  cobalticyanid  of 
potassium  C13(co3K3)N6. 

Platinum  has  a  great  tendency  to  form  a  platinocyanid, 
and  when  the  metal  in  its  spongy  form  is  heated  to  redness 
with  ferrocyanid  of  potassium,  the  mass  yields  to  water  the 
new  salt,  which  crystallizes  in  long  transparent  rhomboidal 
prisms,  yellow  by  reflected  and  blue  by  transmitted  light : 
it  is  C13(Pt3K3)N".  By  decomposing  the  mercurial  salt  with 
sulphuretted  hydrogen,  platinocyanic  acid  Cia(Pt3H3)N8  is 
obtained ;  it  is  very  soluble,  and  crystallizes  in  golden-yel- 
low prisms,  with  a  copper-red  reflection.  The  baryta  salt 
forms  short  lemon-yellow  prisms,  which  are  greenish  by 
reflected  light. 

870.  The  other  complex  cyanids  have  been  but  little  studied : 
one  containing  silver  is  obtained  when  the  oxyd,  chlorid,  or 
cyanid  of  silver  is  added  to  a  solution  of  cyanid  of  potassium. 
The  arcjentocyanid  of  potassium  is  very  soluble,  and  forms 
colorless  tabular  crystals;  its  composition  is  represented  by 
C13(Ag3K3)N6.  It  is  much  less  stable  than  the  previous 
compounds ;  the  silver  is  not  precipitated  by  chlorids,  but 
strong  acids  throw  down  insoluble  cyanid  of  silver,  and  set 
free  hydrocyanic  acid.  With  a  salt  of  lead,  "a  precipitate  is 
obtained  in  which  lead  replaces  the  potassium.  The  silver 
salt  is  used  in  electro-plating,  and  is  generally  prepared  by 
dissolving  oxyd  or  chlorid  of  silver  in  a  solution  of  cyanid  of 
potassium,  hydrate  of  potash  or  chlorid  of  potassium  being 
formed  at  the  same  time.  Oxyd  of  silver  decomposes  even 
the  ferrocyanid  to  form  the  new  double  salt.  In  the  process 
of  electro-silvering,  the  silver  being  liberated  at  one  pole, 
the  potassium  and  cyanic  elements  are  set  free  at  the  other, 
and  this  pole  being  terminated  by  a  plate  of  silver,  the  metal 
is  dissolved  as  fast  as  it  is  deposited  at  the  other  pole,  thus 
preserving  the  strength  of  the  solution. 

Oxyd'of  gold  is  readily  soluble  in  cyanid  of  potassium,  and 
yields  a  double  salt  which  is  used  in  a  similar  manner  to  the 
last  for  the  process  of  electro-gilding.  A  solution  of  cyauid 
of  potassium  may  be  used  to  remove  from  the.skin  or  from 
linen,  the  stains  produced  by  salts  of  silver,  gold  or  mercury. 

ACIDS  OF  THE  URINE  AND  BILE. 

871.  These  animal  secretions  contain  several  peculiar 
azotized  acids,  which  are  very  interesting  from  their  meta- 


504  ORGANIC    CHEMISTRY. 

morphoses  :  those  of  urine  are  named  the  uric  and  Jiippnnt. 
acids. 

The  hippuric  acid  is  found  principally  in  the  urine  of  herbi- 
Torous  animals;  that  of  stall-fed  horses  and  cows  containa 
a  considerable  quantity.  To  obtain  it,  the  fresh  urine  may 
be  mixed  with  chlorohydric  acid  in  the  proportion  of  four 
ounces  of  the  acid  to  a  gallon,  and  allowed  to  stand  for 
some  hours  in  a  cool  place.  A  crystalline  matter  which  is 
deposited  is  impure  hippuric  acid :  it  is  separated,  redis- 
solved  by  boiling  in  water  with  excess  of  milk  of  lime,  and 
a  little  animal  charcoal  to  decolorize  it :  the  filtered  hot 
solution  of  hippurate  of  lime  is  then  mixed  with  a  slight 
excess  of  chlorohydric  acid,  and  hippuric  acid  separates  on 
cooling  in  beautiful  white  prisms.  The  fresh  urine  may 
also  be  heated  to  ebullition  with  milk  of  lime,  and  after 
separating  the  precipitate  thus  formed,  boiled  down  to 
one-tenth,  and  then  precipitated  by  chlorohydric  acid  :  in 
this  way  a  larger  portion  is  obtained,  (from  forty  to  fifty 
grains  from  a  pound.)  Hippuric  acid  is  very  soluble  in 
boiling  water,  but  requires  about  400  parts  of  cold  water 
for  its  solution.  It  is  monobasic  and  is  represented  by 
C1SH0NOB ;  when  boiled  with  peroxyd  of  lead  it  is  converted 
by  oxydation  into  benzamid,  carbonic  acid  and  water: 
C18H(,N00+06  =  C14H?N03+  2C304+ II 302-  %  the  action 
of  nitrous  acid,  hippuric  acid  is  decomposed  like  aspartic 
acid,  and  yields  water,  nitrogen,  and  a  new  acid  called  ben- 
zoylycollic  acid:  it  is  C38H1B016,  two  equivalents  of  hippu- 
ric acid  being  concerned  in  the  reaction.  Benzoglycollic 
acid  is  bibasic  ;  it  is  sparingly  soluble  in  cold  water,  but 
dissolves  readily  in  boiling  water,  alcohol,  and  ether.  It 
fuses  below  212°  F.,  and  at  a  higher  temperature  is  decom- 
posed, benzoic  acid  subliming.  When  boiled  with  dilute 
sulphuric  acid,  it  is  decomposed  into  benzoic  acid,  and  a 
new  bibasic  acid  called  the  glycollic,  C8IIS013.  This  is  homo- 
logous with  lactic  acid,  to  which  it  bears  a  vciy  close  re- 
semblance, and  appears  to  be  identical  with  the  acid  formed 
in  the  preparation  of  the  fulminates.  Beuzo^lycollic  acid 
yields  two  equivalents  of  benzoic,  and  one  of  glycollic  acid  : 
C36H18018+^H80S  =  2CHH604+CsHsOla. 

872.  When  hippuric  acid  is  boiled  with  a  strong  acid,  it 
is  decomposed  into  benzoic  acid  and  a  sweet  crystalline 
substance,  which  was  first  obtained  by  the  action  of  sulphuric 
acid  upon  glue  or  gelatine;  it  has  hence  received  the  name 


URIC   ACID.  505 

of  suga  r  of  gelatine ,  glycycoll,  or  glycocine,  (from  glukus  sweet, 
and  kolla  glue.)  It  is  best  obtained  by  boiling  hippuric 
acid  for  half  an  hour,  in  ten  parts  of  a  mixture  of  sulphuric 
acid  diluted  with  twice  its  volume  of  water.  On  cooling, 
ben  zoic  acid  separates,  and  after  removing  the  sulphuric 
acid  by  saturating  it  with  carbonate  of  lime,  glycocine  re- 
mains in  solution,  and  may  be  purified  by  crystallization  from 
dilute  alcohol.  Glycocine  forms  colorless  prismatic  crystals 
which  are  soluble  in  four  or  fivre  parts  of  water,  but  are  in- 
soluble in  pure  alcohol ;  its  taste  is  sweet,  like  grape  sugar. 
Its  formula  is  C4H5N04,  and  its  formation  from  hippuric 
acid  is  thus  represented;  CuH^OB+HflOa=C«H0O4-f 
C4H5N04.  It  is  homologous  with  alanine,  and  is,  like  it,  an 
organic  base,  forming  salts  which  crystallize  beautifully. 
An  atom  of  hydrogen  in  it  may  be  replaced  by  a  metal,  and 
species  like  C4(H4Cu)N04  are  obtained,  whnh  saturate 
acids,  like  the  normal  glycocine.  Alkargen,  C4H5As04,  the 
product  of  the  oxydation  of  alkarsine,  is  glycocine,  in 
which  arsenic  replaces  nitrogen.  By  the  action  of  nitrous 
acid,  glycocine  is  decomposed  and  yields  glycollic  acid : 
2C4HaN04+2NHO,= N9+2HaOa+CaH9Oia. 

Benzoglycollic  acid  may  be  viewed  as  a  coupled  acid,  in 
which  two  equivalents  of  the  monobasic  benzoic  have  re- 
placed H2  in  the  bibasic  glycollic  acid,  with  the  elimination 
of  2H303;  it  is  therefore  itself  bibasic.  When  a  mixture  of 
benzoic  and  lactic  acids  is  fused  together,  water  is  evolved 
and  the  homologue  of  benzoglycollic  acid,  corresponding  to 
lactic  acid,  is  obtained :  it  is  C40H20016,  and  is  readily  decom- 
posed by  strong  acids  into  benzoic  and  lactic  acids. 

873.  Uric  or  lithic  add  exists  in  the  urine  of  carnivo- 
rous animals,  and  in  that  of  man — in  the  last  associated  with 
hippuric  acid.  The  solid  white  urinary  excretions  of  birds 
and  serpents  are  composed  almost  entirely  of  urate  of  am- 
monia. The  urine  of  the  boa  or  other  serpents  is  dissolved 
by  boiling  in  a  solution  of  hydrate  of  potash,  ammonia 
being  evolved.  A  current  of  carbonic  acid  gas  is  then 
passed  through  the  liquid,  which  throws  down  a  sparingly 
soluble  acid  urate  of  potash.  This  is  washed  with  cold 
water  to  remove  impurities,  and  redissolved  in  a  hot  dilute 
solution  of  potash :  from  the  warm  liquid  chlorohydric 
acid  separates  a  gelatinous  precipitate,  which  soon  changes 
into  a  white  crystalline  powder  of  pure  uric  acid.  The  uric 
cid  may  be  separated  from  the  dung  of  pigeons  or  other 


506  ORGANIC  CHEMISTRY. 

birds  by  a  solution  of  borax  in  100  parts  of  boiling  water: 
the  acid  is  thrown  down  from  this  by  chlorohydric  acid,  and 
may  be  dissolved  in  potash,  and  purified  by  the  process 
already  described. 

Uric  acid  is  soluble  in  2000  parts  of  hot  water,  and  has 
feeble  acid  characters  :  it  is  represented  by  C10H4N406,  and 
is  bibasic;  the  urates,  like  the  acid  itself,  are  sparingly 
soluble.  The  products  of  the  decomposition  of  uric  acid  arc 
numerous  and  interesting.  When  boiled  with  water  and 
peroxyd  of  lead,  carbonic  acid  gas  is  formed,  and  a  substance 
called  allantotn,  which  exists  in  the  amniotic  liquid  of  the 
cow,  and  in  the  urine  of  young  calves.  Its  formula  is 
CSH6N406;  allantoin  forms  brilliant,  colorless  prisms,  soluble 
in  160  parts  of  cold  water.  The  further  action  of  peroxyd 
of  lead  decomposes  it  into  an  oxalate  and  two  equivalents 
of  urea,  C8H8N,Ofl+2HaOa+08=C4H308+2CBH4Na01>, 
Boiled  with  acids  it  fixes  the  elements  of  one  equivalent  of 
water,  and  forms  one  equivalent  of  urea,  and  allanturic  acid 
C0H4N206;  this  is  very  soluble  and  deliquescent.  When 
boiled  with  baryta-water,  allantoin  is  completely  decomposed 
into  an  oxalate  and  ammonia;  C8H6N406-f4(BaH)03+ 
HflOfl=2C4Baa08+4NH?. 

874.  When  uric  acid  is  mixed  with  warm  chlorohydric 
acid  and  chlorate  of  potash  is  gradually  added,  the  acid  is 
dissolved  and  oxydized  at  the  expense  of  the  oxygen  of  the 
chloric  acid.  It  is  converted  by  this  process  into  urea  and 
a  new  compound,  alloxan  C8H4N3010.  This  substance  is  also 
formed  when  uric  acid  is  added  in  small  portions  to  nitric 
acid  of  specific  gravity  1-43;  it  dissolves  with  the  evolution 
of  nitrous  fumes,  mixed  with  nitrogen  and  carbonic  acid 
from  a  partial  decomposition  of  the  urea,  and  on  cooling, 
alloxanis deposited;  C^HAOp+SHA+O^C.HAO.-r- 
CSH4N2010.  Alloxan  crystallizes  in  small  colorless  brilliant 
rhomboidal  crystals,  with  a  vitreous  lustre,  which  are  an- 
hydrous; or  in  large  prisms  which  contain  water,  and  are 
efflorescent.  It  is  very  soluble  in  water,  and  its  solution 
gives  to  the  skin,  after  some  time,  a  purple  stain  and  a 
nauseous  odor.  In  contact  with  bases,  alloxan  combines 
with  H302  to  form  a  feeble  bibasic  acid,  called  the  alloxanic 
acid.  Boiled  with  a  solution  of  baryta  or  with  acetate  of 
lead,  alloxan  fixes  the  elements  of  water  and  yields  urea  and 
a  salt  of  niesoxalic  add,  which  is  soluble,  quadribasic,  and 
represented  by  C6H4013.  If  a  solution  of  alloxan  is  gently 


URIC   ACID.  507 

heated  with  peroxyd  of  lead,  carbonic  acid  gas  is  disengaged, 
and  urea  remains  in  the  solution,  mixed  with  insoluble  oxa- 
late  and  carbonate  of  lead.  Alloxan,  with  water  and  oxygen, 
yields  urea,  carbonic  acid,  and  oxalic  acid ;  C8H4N3010-f- 
Ha03-f  09  =  CaH4NaOa+Cfl04+C4H.,08.  The  carbonate  of 
lead  in  the  residue  results  from  a  further  oxydation  of  a 
portion  of  the  oxalate  by  the  peroxyd. 

875.  When  sulphuretted  hydrogen  is  passed  through  a  solu- 
tion of  alloxan,  sulphur  is  deposited,  together  with  a  white 
crystalline  substance  named  alloxantine;  it  is  C16H10N4Oao, 
and  is  formed  by  the  combination  of  two  equivalents  of  alloxan, 
which  fix  at  the  same  time  H3.    When  a  solution  of  alloxan 
is  mixed  with  chlorohydric  acid,  and  a  fragment  of  zinc  is 
added,  the  hydrogen  from  the  decomposition  of  the  acid  is 
not  evolved,  but  unites  with  the  alloxan  to  form  alloxantine, 
which  crystallizes  upon  the  zinc.    Alloxantine  is  also  formed 
when  a  solution  of  alloxan  is  boiled  with  dilute  sulphuric  or 
chlorohydric  acid,  and  is  deposited  on  cooling ;  an  equivalent 
of  water  is  decomposed,  and  H3  unites  with  two  equivalents 
of  alloxan  to  form  alloxantine,  while  the  03  oxydizes  another 
equivalent  of  alloxan,  as  in  the  case  of  peroxyd  of  lead,  and 
forms  oxalic  and  carbonic  acids  and  urea,   which  last  in 
presence  of  the  acid,  is  decomposed  into  ammonia  and  car- 
bonic acid.     The  decomposition  of  water  in  this  reaction  is 
analogous  to  that  of  sulphuretted  hydrogen  in  the  previous 
process.     This  substance  is  sparingly  soluble  in  water :  it 
appears  to  possess  feeble  acid  properties,  but  is  at  once  de- 
composed  in    contact  with    bases.      When    alloxantine  is 
warmed  with  twice  its  volume  of  water,  and  a  little  nitric 
acid  is  added,  solution  takes  place,  with  the  evolution  of 
nitric  oxyd ;  the  filtered  liquid  mixed  with  a  few  drops  of 
the  acid,  to  oxydize  any  excess  of  alloxantine  in  solution, 
deposits  on  cooling  pure  alloxan;  Cl6H10N4020-|-03  — 2C8H4 
Na010-j-H303.     The  most  advantageous  way  of  preparing 
alloxan  is  to  dissolve  uric  acid  in  warm,  somewhat  dilute 
chlorohydric  acid,  with  the  aid  of  one-fourth  its  weight  of 
chlorate   of  potash,   to  precipitate   alloxantine   by   passing 
sulphuretted  hydrogen  through  the  diluted  solution,   and 
convert  it  into  alloxan  by  the  above  process. 

876.  A  boiling  aqueous  solution  of  alloxantine  is  still 
further    decomposed    by   sulphuretted    hydrogen ;    sulphur 
separates,  and  dialuric  acid  is  formed  ;  this  is  CSH4N20S,  and 
is  monobasic;  its  ammonia  salt  is  colorless,  but   becomes 


508  ORGANIC   CHEMISTRY. 

blood-red  on  drying.  Dialuric  acid  differs  from  alloxan  by 
08,  and  its  potash  salt  is  formed  by  a  process  of  de-oxydation 
when  cyanid  of  potassium  is  added  to  a  solution  of  alloxan. 
By  exposure  to  the  air,  this  acid  absorbs  water  and  oxygen, 
and  is  changed  into  a  dimorphous  form  of  alloxantine. 
Alloxantine  contains  the  elements  of  alloxan,  dialuric  acid, 
and  an  equivalent  of  water;  when  its  solution  is  mixed  with 
one  of  sal-ammoniac,  alloxan  is  formed,  chlorohydric  acid  set 
free,  and  an  insoluble  crystalline  substance  separates,  to 
which  the  name  of  uramile  is  given ;  it  is  the  amid  of  dia- 
luric acid,  being  C8HSN306.  An  equivalent  of  alloxantine, 
C16H10N4Oao+HCl.N  H3=  C.H4N,0M+C.H.N,0,+HC1+ 
2Ha03.  When  a  solution  of  alloxan  is  heated  to  boiling 
with  sulphite  of  ammonia,  it  deposits,  on  cooling,  brilliant 
plates  of  a  new  salt,  the  thionurate  of  ammonia.  Thionuric 
acid  is  bibasic,  and  contains  the  elements  of  alloxan,  am- 
monia, and  sulphurous  acid;  it  is  CsH7N3Sfl014.  When  its 
solution  is  heated  to  boiling,  it  is  completely  decomposed 
into  uramile  and  sulphuric  acid,  C8H5N308-{-SaHa08;  but 
if  previously  mixed  with  sulphuric  acid  and  evaporated  in 
a  water-bath,  dialuric  acid  and  sulphate  of  ammonia  are 
obtained. 

877.  The  solutions  of  uric  acid  in  nitric  acid  are  colored 
of  a  beautiful  purple  by  ammonia;  and  alloxautine  in  an 
ammoniacal  atmosphere,  or  solutions  of  uramile  in  ammonia 
or  hydrate  of  potash,  absorb  oxygen  from  the  air,  and  assume 
the  same  purple  color.  If,  to  a  nearly  boiling  solution  of 
alloxan,  one  of  carbonate  of  ammonia  is  added  in  slight 
excess,  there  is  a  violent  effervescence  from  the  escape  of 
carbonic  acid  gas,  and  the  liquid  assumes  so  deep  a  purple 
hue  as  to  be  almost  opaque.  As  it  cools,  delicate  square 
prisms  are  deposited,  which  are  garnet-red  by  transmitted, 
and  golden-green  by  reflected  light;  their  powder,  under  a 
burnisher,  assumes  a  green  metallic  brilliancy.  This 
beautiful  substance  is  named  murexid,  in  allusion  to  the 
murcx  which  furnished  the  purple  dye  of  the  ancients;  it 
is  slightly  soluble  in  cold  water,  and  colors  it  purple.  Crys- 
tals of  it  are  also  obtained  when  uramile  arid  oxyd  of  silver 
are  boiled  with  water  containing  a  little  ammonia;  the  silver 
is  reduced,  and  the  filtered  purple  solution  deposits  murexid 
on  cooling.  The  probable  formula  of  murexid  is  C8H4N404, 
corresponding  to  the  amid,  or  rather  nitryl  of  alloxauic  acid. 
Alloxanate  of  ammonia,  C8H0N3Oia.2NH3—  4H2Oa^C3H4 


CHOLIC   ACID.  509 

N404.  A  solution  of  murexid  in  hot  water  gives  a  red 
precipitate  with  nitrate  of  silver;  its  solution  heated  to 
boiling  with  sulphuric  acid,  yields  a  precipitate  of  uramile 
and  alloxan,  while  alloxantine  and  sulphate  of  ammonia  re- 
main in  solution. 

When  uric  acid  or  alloxan  is  boiled  with  an  excess  of 
strong  nitric  acid,  carbonic  acid  gas  is  evolved  and  para- 
banic  acid  formed  j  it  is  C8HaN306,  and  is  bibasic  and  very 
soluble.  When  its  ammonia  salt  is  heated  to  boiling,  it 
fixes  H303,  and  is  converted  into  oxalurate  of  ammonia. 
The  addition  of  chlorohydric  acid  to  a  solution  of  the  new 
salt  separates  the  oxaluric  acid  as  a  sparingly  soluble  powder, 
which  is  represented  by  C6H4N308.  When  its  aqueous 
solution  is  boiled,  it  is  converted  into  oxalic  acid  and  urea, 
OflH4N308+H303  =  C4H308+C3H4N303. 

878.  The  action  of  chlorine  upon  the  alkaloid  caffeine, 
produces,  among  other  products,  a  feebly  acid  crystalline 
substance,  sparingly  soluble  in  water,  to  which  the  name 
of  amalic  acid  has  been  given.     It  closely  resembles  allox- 
antine, and  is  homologous  with  it,  being  C24H1SN4030 ;  the 
two  differ  by  4C3H3.      When  amalic   acid   is    moistened 
with  water  and  exposed  to  the  action  of  air  and  ammonia, 
it  is  converted  into  a  reddish-brown  substance,  which,  by 
solution  in  hot  water,  yields  red  crystals,  scarcely  distin- 
guished from  murexid  by  their  characters.     They  are  named 
murexoine,  and  are  probably  the  murexid  of  this  series,  of 
which  the  other  members  have  not  yet  been  studied. 

879.  Cholic  Acid. — The  bile  of  animals  is  a  solution  of 
the  soda  or  potash  salts  of  two  azotized  acids,  one  of  which 
contains  sulphur. «   When  ox-bile  is  evaporated  to  dryness 
and  dissolved  in  alcohol,  the  careful  addition  of  ether  pre- 
cipitates first  the  salt  of  the  sulphur  acid,  and  by  a  further 
addition  of  ether,  aided  by  cold,  the  soda  salt  of  the  dis- 
solved cholic  acid  may  be  obtained  in  crystals.     On  adding 
sulphuric  acid  to  their  aqueous  solution,  the  acid  separates 
after  some  time  in  delicate  white  silky  crystals,  which  have 
a  bitterish  sweet  taste,  and  are  very  sparingly  soluble  in 
water.      Cholic  acid  is  monobasic,  and  is  represented   by 
C5flH43N013.     When  boiled  with  a  solution  of  baryta,  it  is 
decomposed  like  hippuric  acid  into  glycocine  and  a  new 
acid,  containing  no  nitrogen,  which  is  called  cholalic  acid, 

ojByjo!f+Hjlo,===ofHyiro4+c-H40oMf  which  is  the 

formula  of  cholalic  acid.      It  forms  colorless    octahedral 


510  ORGANIC   CHEMISTRY. 

crystals,  which  require  4000  parts  of  cold  water  for  then 
solution,  but  are  very  soluble  in  alcohol.  When  exposed 
to  heat,  or  when  boiled  with  strong  chlorohydric  acid,  it  is 
converted  successively  into  clioloidic  acid  and  an  almost 
insoluble  resinous  body,  dyslysine,  both  of  which  are  formed 
by  the  loss  of  the  elements  of  water  ;  dyslysine  is  C48H36Oa. 
When  cholic  acid  is  heated  with  a  dilute  acid,  it  loses  HflOs, 
and  yields  cliolonic  acid,  C5aH41N010,  which,  by  boiling,  is 
decomposed  into  glycocine,  and  choloidic  acid  or  dyslysine. 

880.  Acetate  of  lead  precipitates  the  cholic  acid  from  bile 
which  has  been  purified  by  solution  in  alcohol,  but  leaves 
in  solution  the  sulphuretted  acid,  to  which  the  name  of 
choleic  acid  is  given  ;  the  bile  of  sheep,  and  of  some  fishes 
is  almost  entirely  composed  of  choleates,  and  that  of  the  dog 
is  pure  choleate  of  soda.  Choleic  acid  resembles  the  cholic 
acid,  but  both  it  and  its  salts  are  more  soluble  in  water. 
Its  formula  is  C5aH43N014S2  ;  when  boiled  with  a  solution 
of  baryta,  it  is  decomposed  like  the  cholic  acid,  and  yields 
cholalic  acid;  and  in  place  of  glycocine,  a  neutral  body 
named  taurine^  which  is  crystalline,  soluble  in  water  and 
alcohol,  and  contains  C4H7NO&Sa.  The  action  of  acids 
yields  taurine  and  cholalic  acid,  and  the  spontaneous  putre- 
faction of  recent  ox-bile,  which  is  mixed  with  the  mucus  of 
the  gall-bladder,  affords  similar  results;  acetic  and  allied 
acids,  probably  froin  the  decomposition  of  glycocine,  accom- 
pany the  taurine,  which  is  itself  decomposed  at  a  later  stage 
of  the  process,  sulphurous  and  sulphuric  acids  being  formed. 

88  i.  The  bile  of  pigs  contains  a  peculiar  acid  to  which 
the  name  of  hyocholic  acid  is  given  :  it  is  CMH43N010,  and 
is  homologous,  not  with  cholic,  but  with  cholonic  acid,  dif- 
fering from  this  by  C3H9:  boiled  with  baryta  water,  it  yields 
glycocine  and  hyochotaiic  acid,  homologous  with  cholalic 
acid  :  by  chlorohydric  acid  it  is  converted  into  glycociue  and 
a  homologous  species  of  dyslysine:  C54H43N010  =  C4H5N04 


Bile  contains,  besides  these  salts,  a  portion  of  fat,  a  yel- 
low coloring  matter,  and  a  neutral  crystalline  body  resem- 
bling spermaceti  in  appearance,  to  which  the  name  of 
c/wlesterine  is  given  :  it  often  forms  concretions  in  the  gall- 
bladder, known  as  biliary  calculi.  The  formula  C^H^O,  is 
assigned  to  it. 


NITROGENOUS  NUTRITIVE  SUBSTANCES.  511 

NUTRITIVE  SUBSTANCES  CONTAINING  NITROGEN. 

882.  Under  this  head  may  be  described  a  class  of  sub- 
stances which  are  common  to  plants  and  animals,  and  sustain 
a  very  important  part  in  the  economy  of  nutrition.     The 
seeds  and  juices  of  all  plants,  in  addition  to  the  starch, 
sugar  and  lignine  always  present,  contain  peculiar  substances 
which,  although  unlike  in  form  and  solubility,  have  a  general 
similarity  of  composition  with   each   other,  and  with  the 
muscular  tissue  of  animals.     The  relations  between  these 
bodies  may  be  said  to  be  analogous  to  those  between  starch, 
gum,  dextrine,  and  lignine.     In  both,  the  differences  are  to 
be  considered  as  in  part  depending  upon  organization,  and 
in  part  upon  that  molecular  arrangement,  which  constitutes 
a  species  of  isomerism.     As  lignine  and  starch  may  be  con- 
verted into  dextrine,  and  as  both  dextrine  and  gum,  by 
acids,  yield  glucose,  so  these  diiferent  azotized  substances 
may  be  converted  one  into  another.     To  these  bodies  the 
general  name  of  protein  compounds  has  been  given,  from 
proteuo,  I  take  the  pre-eminence,  in  allusion  to  their  import- 
ance in  the  vital  economy. 

883.  The  muscle  or  flesh  of  animals  is  called  fibrin,  and  is 
an  organized  form  of  protein ;  fibrin  also  separates  from  the 
blood  during  coagulation,  and  is,  when  pure,  a  white  tasieless 
mass,  insoluble  in  water,  and    becomes   horny  and  translu- 
cent by  drying.     It  dissolves  in  acetic  and  dilute  chloro- 
hydric  acids,  in  warm  solution  of  sal-ammoniac,  nitre,  and 
several  other  salts,  and  is  separated  from  them  by  heat  in 
an  insoluble  amorphous  form. 

The  serum  of  the  blood  and  the  white  of  eggs  contain 
in  solution  a  large  quantity  of  a  protein  compound,  which 
is  similar  in  its  characters  to  dissolved  fibrin,  and  coagulates 
by  a  heat  of  158°  F.  :  it  is  called  albumin,  and  is  nearly 
pure  in  the  white  of  eggs.  Albumin  when  coagulated  by 
heat  is  insoluble  in  water,  and  resembles  fibrin  in  its  chemi- 
cal properties  j  milk  contains  another  soluble  form  of  pro- 
tein, which  is  not  coagulated  by  heat,  but  is  at  once  sepa- 
rated in  an  insoluble  condition  by  a  dilute  acid;  it  has 
received  the  name  of  casein,  and  is  nearly  pure  in  the  curd 
of  skimmed  milk.  Casein  appears  to  be  insoluble  in  water 
when  pure,  and  to  be  held  in  solution  in  milk  by  a  small 
portion  of  soda :  the  albumin  of  the  blood  is  by  the  action  of 
a  solution  of  potash  converted  into  a  form  resembling  casein 


512  ORGANIC   CHEMISTRY. 

884.  When  a  paste  of  wheat  flour  is  washed  with  water 
until  all  the  starch  is  removed,  a  tenacious  gray  substance 
remains,  which  dries  into  a  horny  mass,  and  which,  though 
not  possessed  of  the  organized  structure  of  muscular  fibre,  is 
soluble  in  acetic  acid,  and  is  chemically  identical  with  fibrin  : 
it  is  called  glutin.     The  water  from   the  washing  of  the 
paste,  from  which  the  starch  has  separated  by  repose,  and 
the  juices  of  many  vegetables,  yield  by  heat  an  insoluble 
protein  body,  which  is  vegetable  albumin.     When  beans  or 
peas  are  bruised  witli  water,  a  large  quantity  of  protein  \L 
dissolved,  and  may  be  precipitated  by  the  addition  of  ail 
acid.     It  is  called  legiimin,  or  vegetable  casein. 

885.  When  any  one  of  these  substances  is  dissolved  in  a 
moderately  strong  solution  of  hydrate  of  potash,  and  heated 
for  some  time  to  120°  F.,  the  addition  of  acetic  acid  in  slight 
excess,  separates  a  white  flocculent  matter,  which  when  washed 
with  water  and  dried,  is  a  yellowish  brittle  mass,  soluble  in 
acetic  acid,  but  insoluble  in  water  a-nd  alcohol.     It  is  pro- 
tein in  a  state  of  comparative   purity,  and  has  nearly  the 
same  composition,  from  whatever  source  it  is  obtained.     In 
their  natural  state,  the  protein  bodies  contain  variable  and 
often  considerable  quantities  of  mineral  matter  in  a  state  of 
combination  or  intimate  mixture.    The  curd  of  milk  yields, 
when  burnt,  several  per  cent,  of  ashes,  consisting  principally 
of  phosphate  of  lime.     The  different  protein   compounds 
also  contain  small,  but  variable  proportions  of  sulphur  and 
phosphorus  in  combination  with  the  organic  elements,  pro- 
bably replacing  oxygen  and  nitrogen  in  a  portion  of  the 
protein,  and  the  sulphur  remains  after  solution  in  potash 
and  precipitation  by  acetic  acid.     If  to  a  solution  of  any 
protein  body  in  potash,  a  little  acetate  of  lead  is  added,  and 
the  solution  is  heated  to  boiling,  it  becomes  black  from  the 
formation  of  sulphuret  of  lead;  but  even  by  ebullition  it  is 
difficult  to  decompose  the  whole  of  the  sulphur  compound. 
The  amount  of  sulphur  generally  varies  from  1  to  1-5  per 
cent.,  but  the  protein  from  cows'  horns  and  hoofs  contains, 
according  to  Mulder,  from  3*4  to  4-6  per  cent,  of  that  element. 
The  proportion  of  phosphorus  in  the  different  forms  of  protein 
also  varies  from  a  trace,  to  -8  per  cent.,  and  in  vegetable 
casein  it  rises  to  2-4  per  cent:  it  is  sometimes  absent. 

886.  The  facility  with  which  the  protein  bodies  are  altered 
by  spontaneous  decomposition,  and  by   different  reagents, 
renders  it  very  difficult  to  fix  their  exact  composition.     If 


PROTEIN.  513 

we  suppose  the  sulphur  to  replace  a  portion  of  the  oxygen, 
the  formula  C^H^NgOg  may  be  assigned  as  expressing  very 
closely  the  composition  of  protein.  The  greatest  amount  of 
sulphur  present  in  any  variety  of  protein,  scarcely  amounts 
to  one  equivalent  :  the  normal  protein  appears  to  be  inti- 
mately mixed  with  a  sulphuretted  compound,  which  has 
probably  the  same  equivalent  composition  in  other  respects 
as  protein  itself:  an  analogous  case  occurs  in  the  two  acids 
of  the  bile,  which  can  scarcely  be  separated  from  each  other 
by  any  known  difference  in  properties.  The  phosphorus 
which  is  sometimes  present,  may  belong  to  a  body  in  which 
that  element  replaces  nitrogen,  wholly  or  in  part.  There 
are  other  organic  matters  in  the  brain  and  the  blood,  which 
contain  phosphorus  in  a  similar  combination  ;  but  it  is  more 
probable  that  in  the  protein  bodies,  it  exists  as  phosphate  of 
lime. 

887.  The  following  numbers  give  the  proportions  of 
carbon,  hydrogen,  nitrogen,  and  oxygen,  required  by  the 
above  formula,  and  the  results  of  an  analysis  of  the  protein 
from  albumin,  and  one  of  fibrin.  The  amount  of  oxygen 
equivalent  to  the  sulphur  present,  is  given  on  one  side,  and 
added  to  the  quantity  of  oxygen,  for  the  purpose  of  com- 
parison :  — 

.Analyses  by  Mulder. 
Calculated.        Protein.  Fibrin. 

Carbon  ...........  53-93  53-7  52-7 

Hydrogen  .......  6-36  6-9                            6-9 

Nitrogen  .........  15.73  14-4  15-4 

Oxygen  ...........  23'98  23-6           1  „  .  ,  23-5            )  24., 

Sulphur  ...........  1-4=0-7  |  24  3         l-2=0-6  J  2*  * 

Phosphorus  ...... 


100-00       100-0  100-0 

The  results  of  different  analyses  of  protein  from  other 
sources,  show  still  greater  variations  in  composition,  one 
reason  of  which  is  the  want  of  definite  chemical  characters 
by  which  we  may  be  able  to  separate  it  from  any  admixture 
of  foreign  bodies.  The  above  formula,  however,  coincides 
better  than  any  other,  with  the  analyses  of  the  purest  forms 
of  protein  :  protein  is,  according  to  it,  an  amid,  or  rather  a 
nitryl,  of  cellulose;  CMHwOM+3NHa  =  6HaO£+0»HwN. 
08.  It  should  therefore  under  proper  conditions  assimilate 
water,  and  yield  ammonia,  and  a  body  belonging  to  the 
series  of  cellulose,  dextrine,  or  glucose  ;  in  fact,  when  proteia 

33 


514  ORGANIC  CHEMISTRY. 

is  dissolved  in  strong  heated  chlorohydric  acid,  it  is  com- 
pletely decomposed  into  ammonia,  which  forms  sal-ammoniac, 
and  a  brown  insoluble  matter  identical  with  that  produced 
by  the  slow  decay  of  woody  fibre,  and  derived  from  cellulose 
by  the  loss  of  the  elements  of  water.  A  similar  body  is 
produced  from  grape  sugar  by  the  action  of  chlorohydric  acid. 
The  muscular  tissue  is  insoluble  protein  in  an  organized 
condition,  and  sustains  a  similar  rank  in  the  animal  structure 
to  that  of  cellulose  in  the  vegetal,  while  albumin  and  casein 
are  soluble  unorganized  forms  of  protein,  and  may  be  com- 
pared to  dextrin  and  gum. 

888.  The  action  of  hydrate    of  potash  aided  by  heat, 
upon  the  different  forms  of  protein,  evolves  a  great  deal  of 
ammonia  mixed  with  hydrogen,  and  probably  several  vola- 
tile bases,  and  the  residue  contains,  among  other  substances, 
salts  of  acetic,  butyric,  and  valeric  acids,  and  two  crystal- 
line azotized  bodies,  named  leucine  and  tyrosine.     The  former 
has  the  formula  C13H13N04;  it  is  homologous  with  glyco- 
cine  and  alanine,  and  is  an  organic  base  resembling  these  in 
its  characters.     Tyrosine  is  C^H^NOg.     These  two  bodies 
arc  also  obtained  as  products  of  the  action  of  sulphuric  acid 
upon  protein.     The  protein  bodies  when  mixed  with  water 
and  kept  in    a  warm    place,  readily  undergo  spontaneous 
decomposition,  and  evolve  a   disagreeable  odor,  becoming 
putrid.     Fibrin  is  at  first   converted  into  a  soluble   form 
resembling  albumin,  hydrogen  gas  and  ammonia  are  evolved, 
and  there  remain  in  solution  ammoniacal  salts  of  butyric  and 
valeric  acids,  besides  leucine  and  tyrosin,  and  a  portion  of 
undecomposed  protein. 

889.  When  any  form  of  protein  is  distilled  with  a  mix- 
ture of  bichromate  of  potash  and  sulphuric  acid,  the  latter 
not  being  in  excess,  the  protein  is  oxydized  by  the  chromic 
acid,  and  a  great  variety  of  volatile  products  are  obtained; 
among  them  are  prussic  acid,  or  formic  nitryl,  and  the  nitryl 
of  valeric  acid,  together  with  bitter-almond  oil,  benzoic  acid, 
and  the  formic,  propionic,  butyric,  and  valeric  acids.     When 
peroxyd  of  manganese  is  substituted  for  the  bichromate,  with 
an  excess  of  sulphuric  acid,  the  nitryls  are  not  obtained,  but 
besides  bitter-almond  oil,  and  the  acids  already  mentioned, 
the  acetic  and  caproic  acids,  together  with  the  acetic,  pro- 
pionic, butyric,  and  valeric  aldehyds.     In  the  latter  process 
the  residue  contains  salts  of  ammonia,  and  the  acids  may 
result  from  the  decomposition  of  previously  formed  bodies 


PROTEIN.  515 

liko  leuclne :  this,  when  distilled  with  a  mixture  of  oxyd 
of  manganese  and  sulphuric  acid,  yields  carbonic  acid  and 
valero-nitryl,  and  the  latter  by  an  excess  of  acid  is  con- 
verted into  valeric  acid  ancl  ammonia. 

The  destructive  distillation  of  the  protein  bodies  yields 
a  large  amount  of  carbonate  of  ammonia,  and  a  number  of 
volatile  oily  bases,  some  of  which  are  homologous  with 
ammonia,  besides  water  and  inflammable  gases,  and  leaves 
a  bulky  charcoal  very  difficult  of  combustion,  which  con- 
tains several  per  cent,  of  nitrogen,  and  is  perhaps  a  mixture 
of  carbon  with  something  analogous  to  paracyanogen. 

890.  When  fibrin  or  casein  is  kept  for  some  time  in  a  cool, 
dark,  and  moist  place,  it  undergoes  a  decomposition  which 
results  in  its  partial  or  entire  conversion  into  a  fusible  fat, 
resembling  butter  and  easily  saponified,  which  has  not  yet 
been  minutely  examined.     It  is  said  to  have  a  sweet  taste, 
and  to  be  readily  volatile;  if  such  is  the  case,  it  is  not 
improbable  that  the  product  is  an  ether  of  some  fatty  acid  or 
acids.     This  change  is  observed  in  the  preparation  of  some 
kinds  of  cheese,  and  may  be   supposed  to  consist  in  the 
fixing  of  the  elements  of  water,  the  separation  of  the  nitro- 
gen in  the  form  of  ammonia,  and  a  great  portion  of  the 
oxygen  with  some  of  the  carbon,  in   the  form  of  carbonic 
acid  gas.     It  is  accompanied  with  the  development  of  a 
great  number   of  mycodermic  plants,   or   moulds,   which 
appear  to  be  nourished  by  the  evolved  gases. 

891.  The  protein  bodies  not  only  undergo  spontaneous 
decomposition  themselves  with  great  facility,  but,  under  cer- 
tain conditions,  induce  changes  in  a  great  variety  of  organic 
substances.     The  action  of  casein  in  converting  sugar  into 
acetic  and  lactic  acids,  and  this  latter  into  butyric  and  car- 
bonic acids  and  hydrogen,  and  the  conversion  of  sugar  into 
alcohol   and   carbonic   acid   have  already  been  described. 
Diastase  which  changes  starch   into  sugar,  and  emulsine 
which  effects  the  decomposition  of  salicine  and  amygdaline, 
are  forms  of  protein  or  an  allied  substance. 

If  a  minute  portion  of  putrefying  fibrin  is  added  to  a  solu- 
tion of  leucine,  this  substance  is  decomposed  and  valerate  of 
ammonia  remains  dissolved :  the  spontaneous  decomposition 
of  urea,  hippuric  acids,  and  the  acids  of  the  bile,  in  the  pre- 
sence of  the  putrescent  animal  matters  of  the  secretions,  are 
similar  instances.  These  phenomena  may  be  included  under 
the  general  name  of  fermentations ;  although  the  term  should 


516  ORGANIC   CHEMISTRY. 

be  perhaps  more  restricted  in  its  signification,  and  exclude 
those  processes  in  which  diastase  and  emulsine  are  the  agents. 

892.  The  alcoholic  fermentation  has  heen  the  one  most 
carefully  studied;  it  is  produced  by  decomposing  casein  or 
fibrin,  as  well  as  by  yeast.     Yeast,  when  obtained  from  fer- 
menting beer,  has  a  chemical  composition  allied  to  protein, 
and  resembles  it  in  its  properties ;  it  is  found  under  the 
microscope  to  be  completely  organized,  and  to  consist  of  two 
minute  species  of  fungus,  which  seem  to  be  always  produced 
and  propagated  in  a  solution  of  sugar,  when  undergoing  the 
vinous  fermentation :  the  presence  of  decomposing  protein 
in  a  sugar  solution,  appears  to  excite  fermentation  by  afford- 
ing the  conditions  necessary  to  the  development  and  nutri- 
tion of  these  fungi.    These  bodies  are  figured  in  §  695.    One 
of  the  species  in  yeast  appears  to  be  more  especially  connected 
with  the  vinous  fermentation,  and,  being  much  greater  in  size, 
may  be  separated  by  filtration  from  the  other,  which  is  regard- 
ed as  the  fungus  of  the  lactic  and  butyric  fermentations;  this 
last  also  appears  in  the  conversion  of  casein  into  fat,  and  it  pro- 
duces the  decomposition  of  urea  into  carbonic  acid  and  ammo- 
nia, a  change  which  is  rapidly  effected  in  the  presence  of  yeast. 
The  acetic  fermentation  is  characterized  by  a  distinct  fungus. 

The  power  of  yeast  or  any  form  of  protein  to  produce 
these  organic  changes,  is  destroyed  by  boiling  water,  by 
chlorid  of  mercury,  arsenious  acid,  salts  of  iron,  zinc,  alka- 
lies, mineral  acids,  or  by  oil  of  turpentine  or  kreasote. 
Yeast  may  be  dried  at  a  gentle  heat,  and  regain  its  activity 
when  moistened  with  water,  but  if  when  dried,  it  is  finely 
divided  by  trituration,  so  as  to  destroy  the  fungi,  it  is  inert. 
It  may  be  said  that  whatever  is  fatal  to  the  vitality  of  the 
fungi,  destroys  at  the  same  time  the  activity  of  the  fer- 
ment. The  bodies  just  mentioned  are  known  to  act  as 
antiseptics,  preventing  putrescence,  but  it  is  not  improbable 
that  all  cases  of  putrefaction  belong  to  the  same  class  of 
phenomena  as  these  fermentations. 

893.  From  the  constant  connection  between  the  develop- 
ment of  certain  fungi  and  different  chemical  changes,  it  is 
supposed  by  many  chemists  that  they  are  the  agents  in  the 
process  of  fermentation,  which  is  one  essentially  vital,  and 
that  the  fungi  decompose  the   organic  bodies,  perhaps  by  a 
sort  of  absorption  and  subsequent  excretion. 

The  action  of  boiling  water  and  of  antiseptics,  destroys 
the  power  of  diastase  and  emulsine  to  act  upon  starch  and 


GELATIN.  617 

amygdaline.  I  am  not  aware  whether  in  these  reactions,  the 
development  of  fungi  has  been  noticed.  The  phenomena 
most  analogous  to  fermentations  ope  such  as  those  in  which 
a  small  portion  of  sulphuric  acid  converts  a  large  amount 
of  alcohol  into  ether,  or  olefiant  gas,  and  water,  or  where  the 
same  acid  converts  dextrine  into  sugar,  or  to  the  spontaneous 
decomposition  of  a  solution  of  urea  at  an  elevated  tempera- 
ture :  in  all  these  cases,  the  influence  of  vitality  is  evidently 
excluded.  Our  knowledge  of  chemical  dynamics  appears 
as  yet  inadequate  to  explain  the  part  which  fungi  play  in 
many  processes,  or  to  draw  the  distinction  between  those 
changes  which  appear  to  be  effected  through  their  agency, 
and  those  which  are  purely  chemical. 

894.  Gelatin. — This  substance  exists  in  many  animal  tis- 
sues, as  the  skin,  cellular  membranes,  tendons,  and  ligaments, 
and  forms  the  frame-work  of  the  bones ;  in  this  organized 
form  it  is  insoluble  in  cold  water,  but  by  boiling  it  dissolves, 
and  the  solut::B  forms  on  cooling  a  firm  jelly,  which  is  very 
characteristic   of    gelatin;    this,   when    dried,    constitutes 
ordinary  glue.     The  substance  known  as  isinglass,  is  the 
dried  air-bladder  of  certain  fishes,  and  is  a  nearly  pure  gela- 
tinous tissue,  which  is  soluble   in  boiling  water.     A  so- 
lution of  gelatin  is  precipitated  by  salts  of  mercury,  and 
yields  a  copious  insoluble  precipitate  with  an  infusion  of 
nutgalls,  or  a  solution  of  tannic  acid ;  the  insoluble  tissues 
absorb  tannic  acid  from  its  solutions  to  form  the  same  com- 
pound, which  constitutes  leather.     The  process  of  tanning 
consists  essentially  in  immersing  the  prepared  skin  in  an 
infusion  of  oak  or  hemlock  bark,  by  which  it  is  saturated 
with  tannin,  and  becomes  incapable  of  putrefaction,  insoluble 
in  boiling  water,  firm,  elastic,  and,  to  an  extent,  water-proof. 

895.  Gelatin   undergoes   putrefaction  like  protein,  and 
is  susceptible  of  exciting  fermentation ;  the  products  of  its 
decomposition  by  oxydation,  and  by  the  action  of  acids  and 
alkalies,  are  the  same  with  those  of  protein.     It  however 
yields,  in   addition   to   leucine,   its   homologue,   glycocine 
C4H5N04,  which  was  first  described  by  the  name  of  sugar 
of  gelatin.     When  a  solution  of  gelatin  is  boiled  for  many 
hours  with  dilute  sulphuric  acid,  a  large  quantity  of  sulphate 
of  ammonia  is  formed,  and  the  liquid  contains  sugar,  which 
yields  alcohol  and  carbonic  acid  by  fermentation.     This 
reaction  leads  to  the  supposition  that,  like  protein,  it  is 
nearly    allied   to   dextrin   or  glucose,   and    the    formula 


518 


ORGANIC   CHEMISTRY. 


CjuH^NjOg,  which  accords  closely  with  the  results  of  various 
analyses  of  soluble  and  insoluble  gelatin,  makes  it  corre- 
spond to  an  amid  formed  from  one  equivalent  of  glucose  and 
four  of  ammonia  by  the  loss  of  eight  of  water.  C^H^O^-L 
4NH3  =  C^H20N468-|-8Hap2.  The  decomposition  by  sul- 
phuric acid  will  then  consist  in  the  assimilation  of  water, 
and  the  regeneration  of  glucose  and  ammonia. 

The  gelatinous  substance  obtained  from  cartilage  differs 
somewhat  in  its  composition  and  properties  from  ordinary 
gelatin,  and  has  been  distinguished  by  the  name  of  chondrin. 

THE   BLOOD. 

896.  This  substance  when  recent  is  a  homogeneous, 
slightly  viscid,  red  fluid,  of  a  saltish  taste  and  a  peculiar  odor. 
When  examined  under  a  microscope  it  is  found  to  consist  of 
a  transparent  and  nearly  colorless  liquid,  in  which  are  floating 
an  immense  number  of  small  red  bodies,  (blood  corpuscles,) 
varying  in  form  and  size  in  different  animals,  also  a  small 
and  variable  proportion  of  colorless  globules,  less  in  size  than 
the  red  corpuscles,  to  which  the  name  of  lymph  ylobulcs  is 
given ;  their  real  nature  is  not  well  understood.  Very  soon 
after  the  blood  is  taken  from  the  body,  it  separates  into  a 
red  mass,  called  the  cruor  or  clot,  and  a  yellowish  liquid,  the 
serum.  This  change  is  due  to  the  separation  from  the 
liquid  of  a  portion  of  fibrin,  which  involves,  as  in  a  net,  the 
blood  corpuscles,  and  forms  a  soft  mass  distended  with 
serum.  If  the  blood,  as  soon  as  drawn,  is  stirred  with  a 
branched  stick,  the  fibrin  which  separates,  adheres  in  the 
form  of  white  silky  filaments,  and  the  coagulation  of  the 

blood  is  prevented.  The  same 
result  is  obtained  if  the  recent 
blood  is  mixed  with  three  or 
four  volumes  of  a  saturated 
solution  of  sulphate  of  soda; 
this  holds  the  fibrin  in  solu- 
tion, and  the  red  corpuscles 
separate  unaltered;  they  may 
be  separated  by  a  linen  filter, 
and  washed  from  the  serum 
with  a  solution  of  sulphate  of 
soda,  provided  a  current  of  air 
is  kept  up  through  the  mix- 


Fig.  421. 


hire ,    These  bodies  in  the  blood  of  most  mammiferous  ani- 


BLOOD. 


519 


lg> 


mais  are  red  circular  discs,  with  a  depressed  centre  and  color 
less  exterior;  those  of  birds,  reptiles,  and  fishes  are  elliptical. 
Figure  4'^1  shows  the  blood  discs  of  the  common  frog, 
as  they  appear  under  the  microscope.  The  corpuscles 
in  man  are  very  small,  being  not  more  than  from  -g^1^  to 
ffoW  °f  an  *nck  in  diameter;  those  of  frogs  are  three  or 
four  times  greater  in  their  longer  diameter.  Figure  422  is 
a  microscopic  view  of  the  red 
globules  in  the  blood  of  man; 
they  are  very  similar  to  those 
of  other  mammals;  the  cen- 
tral portions  are  less  brilliant 
than  the  borders.  The  discs 
are  often  seen  resting  upon 
each  other  flatwise,  as  they 
are  represented  at  a  a  a,  and 
more  frequently  edgewise,  as 
at  bb. 

897.  When  placed  in  pure 
water,  the  corpuscles  swell, 
burst,  and  dissolve  into  a  deep 
red  liquid,  which  is  coagulated  by  heat,  and  contains  a  large 
portion  of  protein,  analogous  to  albumin.  The  coloring  mat- 
ter is  separated  from  this  by  ammoniacal  alcohol,  in  which  it 
sdone  is  soluble,  and  is  obtained  by  evaporation  as  a  dark  red- 
brown  mass,  which  is  insoluble  in  pure  water,  but  dissolves 
with  the  aid  of  alkalies,  forming  a  blood-red  solution.  It 
constitutes  but  four  or  five-hundredths  of  the  dried  blood- 
globules,  and  is  called  liematosine.  It  contains  a  large 
portion  of  iron ;  chlorine  separates  the  iron  and  renders  the 
matter  colorless;  an  alkaline  sulphuret  or  sulphuretted 
hydrogen  renders  it  greenish-black,  probably  from  the  sepa- 
ration of  a  metallic  sulphuret,  and  strong  sulphuric  acid  is 
said  to  remove  the  iron,  forming  a  protosalt,  and  leaving  the 
red  color  unaltered.  The  condition  of  the  iron  is  analogous 
to  that  of  this  metal  in  some  salts,  as  in  the  tartrates,  in  which 
it  is  not  precipitated  by  the  ordinary  reagents.  The  coloring 
matter,  according  to  Mulder,  affords  by  analysis, 

Carbon....  66-49 

Hydrogen 5-30 

Nitrogen 10-50 

Oxygen H'05 

•«-  o  a& 

Iron o'oo 

100-00 


520 


ORGANIC   CHEMISTRY. 


898.  The  serum  of  the  blood  is  alkaline,  and  '  )  .tains  a 
large  amount  of  dissolved  albumen,  which  is  coagulated  by 
heat ;  besides  this,  it  holds  in  solution  a  considerable  amount 
of  salts,  which  are  chlorid  of  sodium,  with  sulphates,  phos- 
phates, and  carbonates  of  potash  and  soda,  phosphates  of 
lime  and  magnesia,  and  peroxyd  of  iron.  The  blood  con- 
tains besides  about  1-6  parts  in  1000  of  fatty  substances, 
consisting  in  part  of  ordinary  saponifiable  fats,  and  in  part 
of  a  peculiar  fatty  acid  containing  phosphorus,  besides 
cholesterine,  and  a  fat  named  seroline.  The  following  table 
is  by  Becquerel  and  Ilodier,  and  represents  the  average 
composition  of  healthy  human  blood  of  both  sexes: 


Man. 

Woman. 

Density  of  the  defibrinated  blood  

1-0602 

1-0575 

Density  of  the  serum  

1-0280 

1-0275 

Water  

779-000 

791-100 

141-100 

127-200 

Albumin.                                   .         

69-400 

70-500 

Fibrin  

2-200 

2-200 

Extractive  matters  ) 

6-800 

7-400 

Salts                           J    " 

1-600 

1-620 

Serolino       

•020 

•020 

Phosphuretted  fatty  matter  

•488 

•464 

Cholesterine. 

•088 

•090 

Saponifiable  fat  

1-004 

1-046 

Chlorid  of  sodium  

3-100 

3-900 

Other  soluble  salts  

2-500 

2-900 

Insoluble  phosphates  

•334 

•354 

Oxyd  of  iron  .        ... 

•566 

-541 

The  existence  of  alkaline  carbonates  in  the  blood  has 
been  denied  by  some  chemists,  who  assert  that  its  alkalinity 
is  due  to  the  presence  of  tri basic  phosphate  of  soda.  Traces 
of  fluorid  of  calcium,  oxyds  of  manganese,  lead,  and  copper 
have  been  detected  in  the  blood  of  different  animals,  and 
silica  in  that  of  fowls.  Besides  these,  urea  and  hippurio 
acid  are  found,  and  uric  acid  is  said  to  have  been  detected ; 
in  certain  cases  of  disease,  the  coloring  matter  of  the  bile, 
and  its  fatty  acids,  with  an  increased  quantity  of  cholesterine 
appear  in  the  blood.  After  the  ingestion  of  vegetable  food, 
the  blood  also  contains  a  portion  of  sugar. 


BLOOD.  521 

899.  The  color  of  arterial  blood  is  bright  scarlet,  and  that 
of  the  venous  blood  is  dark  red.     The  blood  of  the  veing 
acquires  the  bright  red  tint  in  the  lungs,  and  loses  it  again 
in  the  capillary  vessels.     These  variations  in  color  depend 
upon  changes  in  the  form  and  condition  of  the  blood  cor- 
puscles, producing  a  difference  in  the  reflection  of  light; 
those  in  arterial  blood  being  convex  and  transparent,  while 
those  in  the  veins  have  become  flattened  and  semi-opaque. 
These  changes  depend  upon  the  action  of  oxygen ;  this  gas 
is  much  more  readily  and  more  copiously  absorbed  by  the 
blood  than  by  water;  the  arterial  blood  of  a  horse  contains 
in  a  state  of  solution  from  J  to  T\j  its  volume  of  gas,  which 
contains  about  four  parts  of  oxygen  to  one  of  nitrogen;  this 
oxygen  disappears  in  the  capillary  vessels,  and  is  replaced 
in  the  venous  blood,  by  carbonic  acid  gas.     When  venous 
blood  is  agitated  in  contact  with  atmospheric  air  or  with 
oxygen,  it  absorbs  this  gas,  and  acquires  the   bright  red 
color  of  arterial  blood;    on  the  contrary,   the  corpuscles 
separated  from  arterial  blood  and  washed  with  a  solution 
of  sulphate  of  soda,  assume  the  dark  red  color  of  venous 
blood   and   become    disintegrated,  dissolving   and   passing 
through  the  filter,  unless  supplied  with  oxygen.     If,  how- 
ever, a  current  of  atmospheric  air  is  passed  through  the 
mixture  upon  the  filter,  the  corpuscles  preserve  their  scarlet 
tint,  and  remain  entire. 

900.  The  globules  of  the  blood  appear  to  be  living  organ- 
isms, which  are  capable  of  resisting  the  dissolving  action  of 
a  solution  of  sulphate  of  soda,  so  long  as  life  remains,  but 
almost  immediately  become  asphyxiated  when  deprived  of 
air,  and  at  once  lose  their  bright  color,  and  yield  to  the  dis- 
solving action  of  the  saline  solution.     The  solutions  of  some 
salts,  as  sal-ammoniac  and  the  chlorid  of  potassium,  prevent 
the  aeration  of  the  blood,  even  in  oxygen  gas. 

The  vitality  of  the  blood,  a  doctrine  as  ancient  as  the 
time  of  Moses,  is  thus  sustained  by  these  facts.  The  sponta- 
neous coagulation  of  the  blood,  when  removed  from  the 
body,  or  in  the  veins  after  death,  is  caused  by  the  separa- 
tion in  an  insoluble  organized  form  of  a  portion  of  dissolved 
protein,  and  seems,  like  the  organization  of  effused  lymph, 
to  be  dependent  upon  an  inherent  vitality  of  the  fluid,  exte- 
rior to,  and  perhaps  independent  of  the  blood  corpuscles. 
The  proportion  of  fibrin  which  thus  separates  is  intimately 
connected  with  the  state  of  the  vital  powers,  and  affords  an 


522  ORGANIC   CHEMISTRY. 

index  to  the  state  of  the  system  in  health  or  disease.  In 
scrofula  and  other  maladies  connected  with  an  asthenic  con- 
dition of  the  system,  the  blood  coagulates  but  feebly,  and 
the  amount  of  fibrin  which  separates  is  much  less  than 
ordinary ;  while  in  inflammatory  diseases,  where  the  action 
of  the  system  is  unduly  heightened,  the  blood  coagulates 
firmly  and  rapidly,  and  the  proportion  of  fibrin  formed  is 
much  greater  than  in  healthy  blood  :  fibrin  constitutes  the 
so-called  huffy  coat  of  the  blood  in  inflammatory  diseases. 
The  normal  quantity  of  fibrin  in  healthy  blood  may  be 
stated  at  from  2-2  to  2-5  parts  in  1000;  while  in  cases  of 
phlegmasia  it  rises  to  6  and  7,  and  in  scrofula  and  the 
latter  stages  of  typhus  is  not  above  1-2  or  2.  In  cases  of 
death  by  lightning,  and  by  certain  poisons,  or  from  a  blow 
upon  the  stomach,  or  even  from  sudden  mental  emotions, 
like  violent  anger,  the  blood  is  found  to  have  lost  the  power 
of  coagulation.  The  blood  corpuscles  are  found  to  diminish 
with  the  proportion  of  fibrin,  and  in  some  cases  of  scrofula 
amount  to  no  more  than  64  to  70  parts  in  1000;  they  are  at 
the  same  time,  small,  pale,  and  irregular  in  shape.  The  pro- 
portion of  globules  is  also  diminished  after  blood-letting  or 
hemorrhages,  and  while  in  acute  diseases  generally,  it  remains 
unaltered,  is  increased  in  plethoric  patients.  The  propor- 
tion of  albumin  and  fibrin  taken  together, generally  remains 
unchanged,  except  in  what  is  called  Bright' s  disease,  when 
the  amount  of  albumin  is  notably  diminished,  a  change  de- 
pendent upon  its  excretion  in  the  urine.  The  mean  com- 
position of  the  blood  in  the  two  sexes  is  seen,  by  the  table 
already  given,  to  be  somewhat  different,  (§  898.) 

901.  The  Flesh  Fluid.— The  recent  muscular  fibre  from 
which  the  blood  has  been  drained,  contains  about  80  per  cent, 
of  watery  fluid,  which  may  be  removed  by  chopping  the  flesh 
and  washing  it  with  cold  water.  The  liquid  thus  obtained,  un- 
like the  blood,  has  an  acid  reaction ;  when  heated,  a  form  of  pro- 
tein resembling  albumin  coagulates;  if  the  acid  liquid  is  then 
neutralized  by  baryta-water,  phosphate  of  baryta  and  phos- 
phate of  magnesia  separate,  and  by  evaporation,  sparingly 
soluble,  colorless  crystals  of  creatin  C8H9N304,  are  deposit- 
ed. This  substance  is  neutral,  but  when  its  solution  is 
evaporated  with  an  acid,  it  loses  H203  and  is  converted 
into  a  crystalline,  strongly  alkaline,  organic  base,  creatinine 
(XH7N802,  which  under  certain  circumstances  unites  with 
and  regenerates  creatin.  When  boiled  with  an  excess 


THE   FLESH-FLUID.  523 

of  caustic  baryta,  creatin  is  decomposed,  ammonia  is  evolved, 
and  a  carbonate  formed,  from  the  decomposition  of  urea; 
the  liquid  affords  crystals  of  sarcosine  C8ELN04.  Creatin 
with  water  yields  urea  and  sarcosine,  C8HgN304-{-Hfl03  = 
C3H4Ns03-f-C6H7N04.  Sarcosine  is  metameric  with  alanine, 
which  it  very  much  resembles  in  its  general  characters, 
and  is  like  it  an  organic  base,  but  is  distinguished  from 
alanineand  its  homologues,  by  subliming  unchanged  at  a  heat 
of  212°  F.  There  are  evidently  two  metameric  series  of 
bases  of  the  type  CnHn_j_1N04,  which  are  represented  by 
alanineand  sarcosine ;  glycocine  and  leucine  appear  to  pertain 
to  the  same  series  as  alanine,  while  the  sulphuretted  base 
thialdine,  C13H13NS4  would  seem  from  its  ready  volatility 
to  belong  to  the  series  of  sarcosine. 

902.  The  flesh-fluid  also  affords  a  peculiar  acid,  called  ino- 
sinic  acid,  which  is  very  soluble  in  water,  and  has  the  peculiar 
flavor  of  broth.     Its  probable  formula  is  C30H14N4022,  repre- 
senting a  bibasic  acid.     The  salts  of  inosinic  acid  crystallize 
beautifully ;  that  of  baryta  is  sparingly  soluble ;  and  those  of 
potash  and  soda  evolve,  when  decomposed  by  heat,  a  strong 
and  agreeable  odor  of  roasted  meat.     Besides  this,  an  acid, 
which  appears  to  be  a  modification  of  lactic  acid,  is  obtained 
from  the  flesh-fluid.     Creatin  has  been  found  alike  in  the 
flesh  of  birds,  beasts,  reptiles,  and  fishes.     Fowls,  which  con- 
tain the  largest  quantity,  furnish  about  y^3^  of  creatin,  and 
about  half  as  much  of  the  inosinate  of  baryta.     Creatin  and 
creatinine  are  also  found  in  the  urine,  and  uric  acid  has 
been  detected  in  the  muscle  of  an  alligator. 

The  flesh-fluid  contains  a  considerable  amount  of  salts, 
principally  alkaline  phosphates  and  chlorids ;  the  salts  of 
potassium  here  predominate,  while  those  of  sodium  are  more 
abundant  in  the  blood. 

903.  Saliva. — This  fluid  in  its  normal  state  is  slightly 
alkaline,  and  contains,  besides  animal  matter,  small  por- 
tions of  salts,  principally  chlorids  and  phosphates  of  alka- 
line bases ;  in  that  of  man  a  small  portion  of  a  soluble 
sulphocyanate  is  found. 

The  pancreatic  juice  is  also  alkaline,  and  analogous  to  the 
ealiva  in  its  composition ;  both  of  these  secretions  contain  in 
solution  an  azotized  organic  substance,  which  may  be  preci- 
pitated by  alcohol,  and  like  diastase  possesses  the  power  of 
rapidly  transforming  a  solution  of  starch  into  dextrine  and 
glucose,  They  are  supposed  in  this  manner  to  exercise  an 


524  ORGANIC   CHEMISTRY. 

important  part  in  preparing  these  substances  for  assimila. 
tion.  The  serum  of  the  blood  has  a  similar  action  upon 
starch. 

904.  The  secretion  of  the  stomach,  called  the  gastric  juice, 
is  acid  in  its  reaction,  and  contains  portions  of  alkaline  chlo- 
rids,  free  lactic  acid,  and  an  azotized  substance  similar  to 
that  of  the  saliva.     It  has  the  power  of  dissolving,  at  the 
temperature  of  the  body,  fibrin,  coagulated  albumin,    and 
other  forms  of  protein,  but  has  no  solvent  action  upon  starch ; 
if  however  the  gastric  fluid  is  rendered  feebly  alkaline,  it  no 
longer  dissolves  protein,  but  acts  upon  starch  like  the  saliva 
and  pancreatic  juice.    In  the  same  way  these,  when  rendered 
acid,  acquire  the  power  of  dissolving  protein.     The  tissue  of 
the  pancreas  from  a  dead  animal,  when  cut  in  pieces  and 
mixed  with  water,  still  exerts  a  solvent  power  upon  starch, 
and  the  lining  membrane  of  the  stomach,  when  digested 
with  water  slightly  acidulated  with  chlorohydric  acid,  forms 
an  artificial  gastric  juice.     The  animal  matter  of  the  gastric 
juice,  which  is  apparently  identical  with  that  of  the  saliva, 
has  been  named  pepsin,  (from  pepto,  I  digest,)  and  like 
diastase  is  at  once  rendered  inactive  by  a  boiling  heat,  and 
by  various  antiseptics.     It  is  analogous  to  the  protein  bodies 
in  its  composition,  and  like  them  has,  under  certain  condi- 
tions, the  power  of  converting  sugar  into  lactic  acid,  and 
thus  changing  its  reaction,  so  as  to  become  capable  of  dis- 
solving protein. 

905.  The  bile  has  already  been  shown  (879)  to  consist  essen- 
tially of  the  soda-salts  of  two  azotized  acids :  besides  these, 
there  are  small  portions  of  alkaline  chlorids  and  phosphates, 
and   some   mucus,  the  azotized    secretion    of   the   mucous 
surfaces.     The  substance  of  the  liver  generally  contains  a 
small  portion  of  sugar.     The  bile  is  alkaline  in  its  reactions, 
and  has  the  power  of  rendering  fats  and  oils  soluble,  acting 
like  a  soap,  and  apparently  fitting  them  for  the  process  of 
assimilation.     The  same  power  is  possessed  by  the  saliva  and 
pancreatic  juice,  which  with  the  bile  and  gastric  juice  are 
brought  in  contact  with  the  food  in  different  parts  of  the 
alimentary  canal,  and  by  their  combined  action  render  the 
amylaceous,  fatty,  and  proteinaceous  portions  of  the  food 
soluble,  and  ready  to  be  elaborated  in  the  form  of  chyle. 
Such,  in  the  present  state  of  our  knowledge,  seems  to  be  the 
nature  and  result  of  the  process  of  digestion. 


CHYLE. — URINE.  525    . 

306.  Cliyle. — This  fluid  in  the  human  body,  as  taken 
up  by  the  lacteals  from  the  small  intestines,  is  white  and 
opake,  and  contains  dissolved  protein  in  a  form  resembling 
albumen,  with  small  globules  of  fat,  to  which  its  milkiness 
is  due,  and  a  portion  of  sugar,  besides  various  salts  and  a 
portion  of  iron  in  a  soluble  form ;  when  first  taken  up  from 
the  intestines,  it  yields  but  very  little  fibrin,  but  the  chyle 
from  the  thoracic  duct  coagulates  like  blood,  yielding  a  clot 
which  contains  fibrin,  and  the  clear  liquid  resembles  the 
serum  of  the  blood,  to  which  this  liquid  is  already  as  it 
were  in  a  state  of  transformation,  wanting  only  the  red 
corpuscles. 

The  solid  excrements  of  animals  contain  portions  of  the 
food,  insoluble  or  unfit  for  assimilation ;  those  of  the  herbi- 
vora  are  made  up  in  part  of  ligneous  matter,  and  those  of 
carnivora  contain  a  portion  of  an  azotized  substance,  and  yield 
ammonia  by  their  decomposition  ;  phosphates  and  other  salts 
are  present  in  considerable  quantity,  in  the  excrements,  and 
render  these  substances  valuable  as  manures. 

907.  Urine. — This  excreinentitious  substance  is  separated 
from  the  blood  by  the  kidneys,  and  removes  from  the  body 
various  salts  and  azotized  matters.  The  latter  are  urea 
and  hippuric  and  uric  acids,  which  have  already  been 
described.  The  urine  of  birds  and  reptiles,  which  is  white 
and  solid,  is  principally  urate  of  ammonia.  That  of  herbi- 
vorous mammals  is  alkaline,  and  contains  in  solution,  besides 
urea,  a  large  amount  of  hippuric  acid;  while  in  carnivora 
this  acid  is  wanting,  and  a  large  amount  of  urea  is  found, 
with  a  little  uric  acid.  This  is  nearly  the  composition  of 
the  urine  of  man  subsisting  upon  a  mixed  diet :  the  average 
quantity  of  urea  in  healthy  human  urine  is  about  3  per 
cent.,  and  that  of  uric  acid  about  y^ou »  ^  a^so  contains  a 
little  hippuric  acid.  When  benzoic  acid  is  taken  into  the 
stomach,,  the  urine  a  few  hours  afterward  is  found  to  con- 
tain a  large  amount  of  hippuric  acid,  apparently  formed  in 
some  way  from  the  benzoic  acid.  Creatin  and  creatinine 
are  also  found  in  urine,  and  that  of  young  .salves  contains 
in  addition  to  a  considerable  quantity  of  creatinine,  a  notable 
amount  of  allantoin.  The  saline  matters  of  the  urine  general- 
ly amount  to  two  or  three  per  cent.,  and  consist  of  chlorid  of 
sodium,  with  sulphates  and  phosphates  of  potash  and  soda, 
And  traces  of  ammoniacal  salts,  besides  phosphates  of  lime  and 


526  ORGANIC  CHEMISTRY. 

magnesia.  Urine  also  contains  a  peculiar  organic  coloring 
matter,  and  a  portion  of  mucus  from  the  blidder,  which  in  a 
few  hours  excites  a  decomposition  of  the  urea,  the  liquid 
becoming  alkaline  from  the  carbonate  of  ammonia  formed. 
If  this  mucus  be  removed  by  filtration,  the  urine  may  be 
preserved  a  long  time  without  change.  When  putrescent 
urine  is  evaporated,  the  ammoniacal  salt  forms  with  the 
phosphate  of  soda,  the  double  phosphate  of  soda  and  ammo- 
nia, which  was  formerly  known  as  the  essential  salt  of  urine, 
or  microcosmic  salt*  If  the  residue  is  evaporated  to  dryness 
and  distilled  at  a  red  heat,  the  acid  of  a  portion  of  phos- 
phate of  ammonia  is  decomposed  by  the  organic  matter 
present,  and  a  small  quantity  of  phosphorus  is  obtained; 
it  was  by  this  process  that  this  curious  element  was  first 
prepared. 

The  fresh  urine  of  man  and  the  carnivora  has  an  acid  re- 
action, which  is  ascribed  to  the  uric  acid  held  in  solution 
by  phosphate  of  soda  :  on  adding  a  little  chlorohydric 
acid  to  the  urine,  the  uric  acid  separates  after  a  few  hours 
in  small  but  distinct  crystals. 

908.  In  disease  the  composition  of  this  fluid  is  sometimes 
altered,  and  the  elements  of  the  chyle  and  blood  find  their 
way  into  the  urine :  in  some  forms  of  dropsy  and  diseases 
of  the  kidneys,  it  contains  albumin,  while  the  urea  is 
deficient,  and  is  found  in  the  blood  and  other  fluids  of  the 
body.  In  other  cases,  all  the  sugar  contained  in  the  food, 
or  formed  in  the  digestive  process  from  starch,  is  excreted 
in  the  urine,  under  the  form  of  glucose,  and  constitutes 
the  disease  called  diabetes  mellitus :  in  this  disease  the  urine 
still  contains  urea  in  large  quantity. 

In  some  states  of  the  system,  the  uric  acid  increasing  in 
quantity,  or  the  solvent  power  of  urine  being  diminished, 
this  acid  is  deposited  in  the  form  of  gravel  or  calculus.  Urio 
acid  or  urate  of  ammonia  constitutes  the  most  common  form 
of  calculus;  but  phosphate  of -lime,  and  the  phosphate  of 
magnesia  and  ammonia,  besides  oxalate  and  more  rarely 
carbonate  of  lime,  are  also  found  as  urinaiy  concretions. 


*  So  named  by  the  older  chemists  as  it  was  then  supposed  to  be  a 
gait  peculiar  to  man.  Man  was  called  the  microcosm,  because  in  hi« 
three-fold  nature  is  repeated  in  miniature  the  order  of  the  universe,  the 
great  koumos  or  macrocosm. 


MILK. 


527 


909.  Milk. — This  secretion 
of  the    female    contains  in  a 
soluble  form  all  the  substances 
necessary  for  the  nutrition  of 
the  young, — protein,  fat,  su- 
gar, and  various  salts.     When 
viewed  under  the  microscope, 
milk  is  seen  (fig.  423)  to  con- 
tain numerous  globules  of  fat 
suspended   in   a  clear  liquid ; 
these  globules  are  butter,  and 
give  to  milk  its  opacity.     The 
proportions  of  its  ingredients 
vary,  but  the  following  analy- 
sis of  cow's  milk  may  be  taken  as  an  example  : — 1000  parts 
contain, 

Water 873-0 

Butter 30-0 

Casein,  and  a  little  albumin 48-2 

Milk-sugar,  or  lactose 43.9 

Phosphate  of  lime,  with  a  little  fluorid  of  calcium 2-3 

Chlorids  of  potassium  and  sodium 1'7 

Phosphate  of  iron  and  magnesia,  with  a  little  soda  com- 
bined with  casein *9 

1000-0 

Woman's  milk  contains  proportionably  more  sugar  and 
less  casein,  and  in  these  respects  it  resembles  asses  milk, 
which  also  contains  but  little  butter  :  the  milk  of  carnivora 
like  wise  contains  a  considerable  proportion  of  sugar,  even  when 
the  animals  have  been  fed  for  a  long  time  exclusively  on  flesh. 
It  is  in  this  case  probably  derived  from  the  transformation 
of  gelatin  or  protein,  in  the  manner  already  pointed  out; 
and  the  lactic  acid  in  the  flesh-fluid  of  carnivora  must  have 
a  similar  origin. 

910.  When  milk  is  saturated  with  common  salt  and  filtered, 
a  clear  liquid  is  obtained,  which  holds  in  solution  the  casein, 
sugar,  and  salts;  while  the  butter  rests  upon  the  filter  in  tho 
form  of  globules,  which  are  enclosed  in  an  albuminous  mem- 
brane, and  are  insoluble  in  ether.     If,  however,  the  milk  is 
first  boiled,  the  albuminous  coating  appears  to  be  dissolved, 
and   the  whole  of  the  butter  is  dissolved  by  agitation  with 
ether,  leaving  the  milk  transparent.  After  a  few  hours'  repose 
the  greater  part  of  the  globules  rise  to  the  surface  in  the  form 
of  cream.     In  describing  casein,  (875,)  the  effect  of  acids  ia 


628  ORGANIC    CHEMISTRY. 

producing  the  coagulation  of  milk  has  been  already  noticed : 
*he  whey  contains  all  the  sugar,  and  the  soluble  salts.  Th« 
spontaneous  coagulation  of  milk  depends  upon  the  forma- 
tion of  a  little  lactic  acid  from  the  sugar :  in  the  prepara- 
tion of  cheese,  an  infusion  of  the  lining  membrane  of 
a  calf's  stomach,  called  rennet,  is  added,  which  causes  an 
almost  immediate  separation  of  the  casein  in  an  insoluble 
form ;  this  reaction  does  not  depend  upon  the  formation  of 
lactic  acid,  but  may  take  place  in  the  presence  of  an  excess 
of  alkali ;  milk  in  its  recent  state  has  an  alkaline  reaction. 
In  cheese  which  has  been  long  kept,  there  are  found  seve- 
ral products  of  the  decomposition  of  casein,  among  which 
are  salts  of  butyric  and  valeric  acids,  and  probably  leucine  j 
besides  butter  from  the  milk,  cheese  often  contains  a 
portion  of  fat,  from  the  transformation  of  the  casein  already 
described. 

911.  Eyys. — The  white  part  of  the   eggs  of  fowls  con- 
sists of  a  solution  of  albumin,  with   small   quantities   of 
soda  and  various  salts :  on   boiling  eggs,  a  portion  of  sul- 
phur, from  the  albumin,  combines  with  soda  to  form  a  sul- 
phuret  of  sodium,  which  is  recognized  by  the  blackening  of 
a  piece  of  bright  silver.     The  yolk  of  eggs  contains,  besides 
a  protein   compound,  a  large  portion  of  oil   which  consists 
principally  of  oleine  and  margarine,  and  a  peculiar  viscous 
matter  which  contains  ammonia,  and  yields,  by  the  action  of 
acids,  oleic  and  margaric  acids,  and  a   soluble  acid  which 
appears  to  contain  the  elements  of  phosphoric  acid    and 
glycerine.     Besides  these, lactic  acid  and  the  salts  which  are 
found  in  the  blood   and  flesh-fluid,  are  present. 

912.  The  brain  and  nervous  substance  are  similar  in  their 
chemical  nature,  and  the  white  and  gray  portions  of  the 
brain  differ  chiefly  in   their  structure ;  they  contain  about 
80  per  cent,  of  water.     The   solid  matter  consists  in  part 
of  a  protein  body,  and  in  part  of  a  substance  which,  by 
the  action  of  acids,  yields  products  similar  to  the  viscous 
matter  of  the  yolk  of  eggs.     Besides  these  there  is  present 
»  fatty  crystalline  acid,  which  contains  nitrogen  and  about 
one  per  cent,  of  phosphorus,  and  has  been  named  cerebric 
jLcid.     It  is  but  little  known,  but  is  probably  somewhat 
analogous  to  the  acids  of  the  bile.     It  appears  to  be  identi- 
cal with  the  phosphurettcd  fat  of  the  blood  j  cholesterine 
is  also   present  in  the  substance  of  the  brain,   besides  an 


BONES.  529 

oily  fat  acid,  which  appears  to  contain  the  elements  of  phos- 
phoric and  oleic  acids.  The  solid  matter  of  the  brain  con- 
tains about  four  per  cent,  of  phosphorus. 

913.  Bones. — The  bones  consist  of  a  tissue  of  insoluble 
gelatine  enveloping  a  large   amount  of  earthy  salts.     The 
bones  of  young  animals  contain  but  a  small  portion  of  mine- 
ral matter,  which  increases  with  their  growth.     A  deficiency 
of  the  solid  ingredients  occurs  in  rickets,  and  other  diseases 
connected  with  defective  nutrition.     The  dried  bones  of 
adults  contain  from  30  to  40  per  cent,  of  organic  matter, 
which  is  almost  entirely  soluble  in  boiling  water ;  water  also 
removes  small  quantities  of  salts  of  soda.     The  remainder, 
is  principally  tribasic  phosphate  of  lime  P05.3CaO,  with 
small  portions  of  phosphate  of  magnesia,  carbonate  of  lime, 
and  fluorid  of  calcium.     The  two  analyses  which  follow  are 
of  a  human  femur  and  the  femur  of  an  ox : — 

Man.  Ox. 

Phosphate  of  lime 58-30  59-67 

Phosphate  of  magnesia......' 2-09  1-21 

Carbonate  of  lime 7'07  G-39 

Fluorid  of  calcium 2-73  2-05 

Organic  matter 30-58  31-11 

10CW  100-43 

When  a  bone  is  immersed  in  a  dilute  acid,  as  the  chloro- 
hydric,  the  earthy  salts  are  entirely  removed,  and  the  bone 
becomes  translucent  and  flexible.  It  then  dissolves  in  boil- 
ing water,  leaving  only  a  small  portion  of  insoluble  tissue, 
consisting  of  the  blood-vessels  which  penetrated  its  sub- 
stance, and  which  are  composed  of  protein.  The  horns  of 
the  deer  are  analogous  to  bones  in  composition ;  the  tusks  of 
the  elephant,  which  constitute  ivory,  and  the  teeth,  are  very 
similar  :  the  latter  contain  less  organic  matter  than  bones, 
and  in  the  enamel  of  the  teeth,  which  contains  a  considera- 
ble amount  of  fluorid  of  calcium,  the  animal  matter  is 
absent. 

914.  The  horns  of  cattle,  which,  unlike  those  of  the  deer, 
are  flexible  and  softened  by  heat,  are,  like  the  hoofs  of  ani- 
mals, composed  of  a  protein  body  containing  a  large  amount 
of  sulphur.     The  skeletons  of  zoophytes  and  the  shells  of 
mollusks  contain  a  small  quantity  of  animal  matter,  with 
carbonate  of  lime  and  small  portions  of  phosphates  of  lime 
and   magnesia  and  fluorid  of  calcium.       Those   of   many 
crustaceans  consist  principally  of  phosphate  of   lime  with 
a  little  magnesia  and  carbonate  of  lime. 

34 


530  ORGANIC   CHEMISTRY. 

When  the  leather-like  coating  of  the  salpce  and  some  other 
tunicate  mollusks  is  digested  with  a  solution  of  potash,  the 
nervous  and  muscular  portions  are  dissolved,  and  the  in- 
soluble residue  contains  no  nitrogen,  and  appears  identical 
in  composition  to  the  cellulose  of  plants. 


NUTRITION  OF  PLANTS  AND  OF  ANIMALS. 

915.  IN  the  order  of  nature,  the  animal  creation  derives 
its  support  from  the  vegetable,  whose  products  are  directly 
or  indirectly  the  food  of  the  former.     A  large  number  of 
animals  subsist  upon  herbs  or  grains,  and  the  flesh  of  these 
vegetable  feeders  is  the  food  of  carnivorous  animals.    Plants 
have  the  power  of  forming  from  carbonic  acid,  water,  and 
ammonia,  those  bodies  of  the  carbon  series  which  are  neces- 
sary for  the  support  of  animals.     The  nutrition  of  plants 
may  then  be  properly  considered  first  in  order. 

916.  The  organic  substances  essential  to  plants  are  cellu- 
lose and   protein,  to  which  we  may  perhaps  add    starch; 
these  go  to  make  up  the  simplest  vegetable  structure,  and 
neither  of  them  are  probably  ever  wanting.     In  addition  to 
these   are   sugar,  gum,   oils,   resins,  acids,  alkaloids,  and 
many  other  substances,  some  one  or  more  of  which  are  gene- 
rally present  in  different  parts  of  plants.     The  history  of 
the  related  series  of  cellulose,  starch,  sugar,  and  gum,  and 
of  the  protein  compounds,  has  been  already  given.     These 
bodies  in  their  organized  forms  always  contain  small  and 
variable  portions  of  salts  of  potash,  soda,  lime,  and  magnesia, 
with  chlorine,  phosphoric,  sulphuric,  and  silicic  acids.    The 
juices  of  plants  contain  these  same  salts  in  solution,  some- 
times with  the  addition  of  those  of  ammonia,  and  various 
vegetable  acids,  either  free  or  in  the  form  of  salts.     Theso 
mineral  ingredients  appear  essential  to  healthy  development; 
they  perform,  however,  but  a  secondary  part  in  the  nutrition 
of  plants,  whose  food  consists  essentially  of  water,  carbonic 
acid,  and  ammonia,  from  which,  as  has  been  already  said, 
they  form  the  various  organic  substances,  by  the  combina- 
tion of  certain   molecules  and  the  elimination  of  certain 
others,  in  a  manner  similar  to  that  which  we  have  so  often 
illustrated  in  the  preceding  pages. 


NUTRITION   OP  PLANTS   AND   ANIMALS.  531 

917.  Cellulose  and  the  allied  substances    contain  pre- 
cisely the  elements  of  carbon  and  water,  and  may  be  formed 
from  the  elements  of  carbonic  acid  gas  and  water,  cr  rather 
from  hydrated  carbonic  acid  C3Ha06,  by  the  separation  of 
oxygen;  12dX08=0JWHfl0Ofl0+04S.     Protein,  which  we 
have  shown  may  be  regarded  as  the  amid  of  cellulose,  is 
formed  with  the  concurrence  of  the  elements  of  ammonia, 
in  a  manner  which  will  be  at  once  understood.     Sugar  and 
gum  differ  from  cellulose  only  by  the  elements  of  water, 
and  the  various  vegetable  acids  and  other  matters  contain- 
ing oxygen,  hydrogen,   and  carbon,  may  be  formed  in  a 
manner  analogous  to  cellulose  from  carbonic  acid  and  water, 
by  the  separation  of  oxygen.     It  is  probable  that  the  saline 
and  alkaline  matters  in  the  juices  exercise  peculiar  influences 
upon  these  processes,  and  conduce  to  the  formation  of  the 
various  products. 

918.  The  oxygen  set  free  in  all  these  processes  is  evolved 
in  the  form  of  gas.     If  a  branch  of  a  green  healthy  plant  is 
exposed,  under  an  inverted  bell-glass  filled  with  water,  to 
the  sun's  rays,  minute  bubbles  of  gas  appear  upon  the  leaves, 
and  rise  to  the  top  of  the  vessel.     They  are  pure  oxygen, 
which  is  constantly  evolved   by  all  healthy  plants  when 
exposed  to  the  influence  of  light.     In  darkness,  the  action 
is  suspended  or  imperfectly  performed,  and  the  carbonic  acid 
which  is  absorbed  by  the  roots,  is  given  off  from  the  leaves 
instead  of  oxygen ;  the  leaves  of  plants  also  exhale  large 
quantities  of  water.      Although  it  is  principally  through 
the  roots  that  carbonic  acid,  water,  and  ammonia  are  taken 
up,  the  leaves  have  also  the  power  of  absorbing  water  and 
gases  for  the  support  of  the  plant. 

If  a  plant  is  made  to  grow  in  a  mixture  of  oxygen  and 
carbonic  acid  gases,  the  latter  is  gradually  absorbed  and 
replaced  by  pure  oxygen.  Flowers  and  fruits,  during  the 
period. of  their  growth,  however,  reverse  this  process,  and 
absorb  oxygen  from  the  atmosphere,  while  they  evolve  car- 
bonic acid  gas. 

919.  The  atmospheric  waters  falling  upon  the  earth,  con- 
tain in   solution  a  portion  of  carbonic  acid  and  a  minute 
quantity  of  carbonate  of  ammonia,  two  ingredients  which 
are  always  present  in  the  atmosphere.     The  water  dissolves 
from  the  soil  a  minute  portion  of  earthy  and  alkaline  salts, 
which  are  in  part  set  free  by  the  disintegration  of  the  earthy 
minerals  under  the  influence  of  water  and  carbonic  acid 


532  ORGANIC   CHEMISTRY. 

In  this  form  the  different  elements  are  taken  up  by  tho 
rootlets  of  the  plant,  and  while  the  carbonic  acid  and  am- 
monia are  assimilated  in  the  way  that  we  have  seen,  tho 
sulphates  and  phosphates  furnish  the  portions  of  sulphur 
and  phosphorus  contained  in  vegetable  protein,  while  their 
alkaline  bases  with  the  vegetable  acids,  form  salts,  which, 
being  decomposed  by  heat,  are  the  source  of  the  alkaline 
carbonates,  always  found  in  the  ashes  of  vegetables.  The 
bitartrate  of  potash  in  the  juice  of  grapes  is  an  example 
of  the  occurrence  of  an  organic  potash  salt. 

920.  Careful  analyses  of  their  ashes  have  shown  that  the 
nature  and  proportions  of  saline  matters  differ  greatly  in 
different  plants,  and  that  the  long-continued  cultivation  of 
any  species  of  plant  upon  the  same  soil  may  so  far  exhaust 
the  soluble  mineral  matter  as  to  render  the  soil  unfruitful. 
In  such  circumstances,  its  fertility  may  be  restored  by  the 
application  of  mineral  manures,  such  as  bone-dust,  gypsum, 
and  wood-ashes.     A  soil  which  has  become  unfitted  for  the 
growth  of  one  plant  may  still  contain  the  mineral  substances 
necessary  for  the  support  of  another,  and  hence  the  utility 
of  an  alternation  of  crops  in  agriculture.     The  ashes  of 
tobacco  contain,  for  example,  a  large  amount  of  potash  salts, 
and  those  of  wheat  and  other  cereal  grains  abound  in  phos- 
phate of  lime,  and  contain  but  little  potash ;  so  that  a  soil 
unfitted  for  tobacco  may  still  produce  good  wheat,  and  vice 
versa.     Many  plants  which  grow  in  the  vicinity  of  the  sea 
contain  a  large  amount  of  salts  of  soda;  such  are  those  that 
afford  the  impure  alkali  kelp  or  barilla.     The  amount  of 
mineral  matter  in  many  of  the  fucoids  or  sea-weeds  is  very 
large,  and  the  quantity  of  potash  which  they  contain  some- 
times exceeds  that  of  the  soda ;  a  fact  which  shows  the  curious 
power  of  plants  to  choose  certain  elements  in  preference  to 
others,  for  the  proportion  of  potash  salts  in  sea-water  is  very 
small.     The  ashes  of  marine  plants  are  also  remarkable  for 
containing  salts  of  iodine,  an  element  which   cannot  be 
detected  in  sea-water,  but  is  contained  in  considerable  quan- 
tity in  the  plants  growing  therein,  and  is  even  present  in 
traces  in  many  fresh-water  plants. 

921.  Fertile  soils  generally  contain  a  portion  of  organic 
matter,  derived  from  the  decomposition  of  roots,  leaves,  and 
other  vegetable  substances,  and  approaching  to  what   hag 
been  named  humus  or  humic  acid.     This  substance  by  its 
slow  decomposition  constantly  evolves  carbonic  acid,  and  is 


NUTRITION   OP  PLANTS   AND   ANIMALS.  533 

thus  a  source  of  carbon  to  the  roots  of  plants.  This  organic 
matter  also  contains  in  its  substance  the  various  salts  neces- 
sary for  plants,  and  during  its  decay,  sets  them  free  in  a 
soluble  form.  It  is  still  further  efficient  by  the  power  which 
it  possesses,  in  common  with  charcoal,  clay,  and  other  poroua 
substances,  of  absorbing  the  ammonia  contained  in  the  air  or 
evolved  from  the  decomposition  of  azotized  matters,  and 
holding  it  in  such  a  form  that  it  is  dissolved  out  by  atmo- 
spheric waters,  and  brought  to  the  roots  of  plants.  It  would 
also  appear,  from  the  experiments  of  Mulder,  that  humus 
possesses  the  power  of  forming  ammonia  with  the  nitrogen 
of  the  air. 

922.  Some  chemists  maintain  that  soluble  forms  of  humus 
are  directly  absorbed  by  the  roots,  and  thus  constitute  their 
food  :  there  are  however  no  proofs  of  such  an  absorption,  and 
many  arguments  against  it.     It  is  well  established  that,  if 
supplied  with  atmospheric  waters  and  the  proper  mineral 
ingredients,  plants  will  flourish  and  mature  their  seeds  in 
a  soil  destitute  of  organic  matter.     Many  plants  are  para- 
sitic, and  grow  without  any  connection  with  the  soil ;  they 
may  be  suspended  in  the  air,  and  will  continue  to  grow  for 
years,  absorbing  food  through  their  leaves,  and  generating 
cellulose,  protein,  and   other   organic   bodies.     The   small 
portion  of  mineral  matter  which  these  plants  contain,  may 
be  derived  from  the  solution  and  absorption  of  the  dust 
floating  in  the  air. 

In  the  process  of  germination,  the  albumin  of  the  moisten- 
ed seed  becomes  soluble,  and  its  starch  is  converted  jnto 
sugar  :  these  substances  serve  to  nourish  the  embryo  plants, 
but  when  the  roots  and  leaves  are  fully  formed,  the  plant 
begins  a  new  mode  of  life.  Its  carbon  is  derived  from 
carbonic  acid,  and  the  decomposing  organic  matters  of  the 
soil  serve  only  as  sources  of  carbonic  acid,  ammonia,  and 
salts.  -We  have  seen  how  some  of  the  fungi  excite  the 
decomposition  of  protein  and  sugar  solutions,  apparently 
assimilating  a  portion  of  the  evolved  carbonic  acid  and  ammo- 
nia, and  it  is  not  improbable  that  the  rootlets  of  the  higher 
orders  of  plants  may  act  in  a  like  manner  upon  the  organic 
matters  in  the  soil,  thus  accelerating  their  decomposition. 

923.  Animal  matters  act  beneficially  as  manures,  by  the 
ammonia  which  they  evolve  with  the  carbonic  acid,  in  the  pro- 
cess of  decay.     Bone-dust  in  addition,  affords  phosphates; 
and  urine,  besides  its  ammonia,  contains  a  great  variety  of 


534  ORGANIC   CHEMISTRY. 

earthy  and  alkaline  phosphates,  and  chlorids.  Dilute  solu- 
tions of  sulphate,  or  other  salts  of  ammonia,  act  as  powerful 
stimulants  to  vegetation,  and  the  efficacy  of  guano,  which  is 
the  decomposing  excrement  of  sea-birds,  is  due  in  great  part 
to  the  ammonia  which  it  yields.  In  its  recent  state  it  con- 
tains besides  inorganic  salts  a  large  portion  of  urate  of 
ammonia,  from  which,  during  decomposition,  oxalate  and 
other  salts  of  ammonia  are  formed.  Wheat  manured  with 
guano  is  said  to  contain  a  larger  proportion  of  protein  than 
that  grown  upon  the  same  soil  without  the  manure.  The 
efficacy  of  gypsum  depends  in  part  upon  its  furnishing  lime 
and  sulphates  to  plants,  and  in  part  apparently  from  its 
power  of  condensing  and  retaining  in  the  form  of  sulphate, 
the  ammonia  from  the  air  and  other  sources.  The  ammo- 
nia contained  as  carbonate  in  atmospheric  waters  being 
brought  in  contact  with  earthy  salts  in  the  soil,  must  always 
be  brought  to  the  roots  of  the  plants,  in  the  form  of  sulphate 
or  chlorid,  or  as  a  soluble  ammonia-magnesian  salt. 

924.  The  food  of  animals,  whether  they  feed  upon  flesh, 
or  upon  vegetable  substances,  consists  of  protein  in  its  vari- 
ous forms,  starch,  sugar,  gum,  and  fat,  to  which,  in  the  case 
of  carnivorous  animals,  gelatine  is  to  be  added.     The  vege- 
table feeders  convert  the  protein  bodies  of  their  food  into 
muscular  fibre,  which  is  afterward  the  food  of  the  carnivora. 
These  protein  compounds,  which  can  alone  form  blood  and 
muscle,  are  to  be  distinguished  from  the  non-azotized  por- 
tions of  the  food,  and  have  been  called  the  plastic  elements 
of  nutrition,  in  distinction  from  the- latter,  which  are  named 
the  plastic  elements  of  respiration,  being  consumed  in  that 
process.     Gelatine  probably  belongs  to  the  latter  class ;  it 
has  never  been  found  in  the  blood,  and  is  supposed  to   be 
converted  into  sugar  and  ammoniacal  salts. 

925.  The  power  of  producing  from  simpler  bodies,  the 
complex  organic  products,  does  not  belong  to  the  animal 
system.     The  process  of  digestion  has  already  been  briefly 
described ;  the  saliva,  bile,  gastric  and  pancreatic  juices  exert 
upon  the  food  an  essentially  disorganizing,  destroying  action, 
which  reduces  it  to  a  soluble  plastic  form,  fit  for  assimila- 
tion, in  which  process  the  protein  assumes  an  organic  struc- 
ture, and  forms  blood  and  muscular  fibre,  while  gelatine  is 
probably  formed  from  a  portion  of  it,  by  a  reaction  not  well 
understood.     The  sugar  contained  in  the  food  or  formed 
from  the  starch,  appears  to  be  in  great  part  absorbed  by 


NUTRITION   OP   PLANTS   AND   ANIMALS.  535 

the  coats  of  the  stomach  and  small  intestines,  in  the  same 
way  as  water  and  saline  fluids,  and  thus  finds  its  way  into 
tne  veins,  without  passing  through  the  chyle-duct.  It  is 
directly  oxydized  in  the  circulation,  and  in  a  few  hours 
after  its  ingestion  disappears  entirely  from  the  blood.  Alco- 
hol is  absorbed  in  the  same  way,  and  oxydized  in  the  circu- 
lation, being  converted  into  water  and  carbonic  acid.  Ace- 
tic acid  has  been  found  in  the  blood  as  an  intermediate 
product  of  the  oxydation  of  alcohol,  and  formic  acid  is  said 
to  have  been  detected  after  the  ingestion  of  sugar. 

The  fat,  which,  with  the  protein,  passes  through  the  chyle 
into  the  blood,  is  deposited  in  the  adipose  tissues  :  besides 
that  contained  in  the  food,  it  is  probable  that  fat  is  formed 
by  some  process  from  the  other  aliments;  its  spontaneous 
production  from  protein  has  been  already  described,  and  we 
have  seen  how  fatty  acids,  like  the  butyric,  valeric,  and 
capric,  may  be  formed  from  sugar,  and  by  the  oxydation  of 
protein.  To  these  considerations  may  be  added  some  ex- 
periments which  seem  to  show  that  geese,  in  the  process  of 
fattening,  secrete  a  greater  amount  of  fat  than  is  contained 
in  the  food  which  they  consume. 

926.  It  has  been  shown  that  the  blood  in  the  lungs  dis- 
solves a  large  portion  of  oxygen  gas.  The  cells  of  that 
organ  are  filled  with  air  in  the  process  of  respiration,  and 
the  minute  branches  of  the  pulmonic  artery  are  spread  over 
the  walls  of  the  cells.  The  delicate  arterial  membrane  being 
permeable  to  gases,  oxygen  is  absorbed  and  carbonic  acid 
gas  given  off  through  it.  The  use  of  the  oxygen  in  the 
oxydation  of  sugar  and  alcohol  has  already  been  shown ; 
the  whole  of  the  oxygen  absorbed,  is  not  given  out  in  the 
form  of  carbonic  gas,  but  is  in  part  exhaled  as  aqueous 
vapor  from  the  lungs,  and  from  the  skin. 

There  is,  in  addition  to  this  oxydizing  process,  a  constant 
action-  going  on  in  the  tissues,  which  results  in  their  disor- 
ganization and  conversion  into  simpler  forms.  This  is 
effected  in  the  capillary  vessels  with  the  concurrence  of  the 
dissolved  oxygen  of  the  arterial  blood;  protein  is  decomposed, 
with  the  addition  of  oxygen,  into  a  set  of  highly  carbonized 
bodies,  the  fatty  acids  of  the  bile ;  and  of  highly  azotized  sub- 
stances, urea  and  uric  acid,  which  are  carried  by  the  veins 
to  the  liver  and  kidneys,  and  are  separated  from  the  blood; 
in  the  one  case  to  be  voided  in  the  urine,  and  in  the  other 
to  be  returned  to  the  alimentary  canal;  and  there  to  perform 


536  ORGANIC   CHEMISTRY. 

gome  part  in  the  nutritive  process.  It  is  not  improbable 
that  the  acids  of  the  bile  may  be  converted  into  ordinary 
fats,  which  are  thus  indirectly  formed  from  the  protein 
tissues.  Lactic  acid  on  the  one  hand,  and  creatin  and  in- 
osinic  acid  on  the  other,  are  also  products  of  this  metamor- 
phosis, which  has  been  called  the  destructive  assimilation. 
Its  relation  to  the  matter  of  the  brain  and  nerves  is  not  yet 
well  understood. 

927.  The  oxydation  of  fat,  by  which  it  is  converted  ulti- 
mately into  carbonic  acid  and  water,  does  not  probably  take 
place  in  the  circulation,  as  in  the  case  of  sugar,  but  is  effected 
through  the  capillary  vessels,  in  the  tissues  where  the  fat 
has  previously  been  deposited.     When  the  amount  of  sugar, 
and  farinaceous  food  is  great,  animals  grow  fat,  for  the  glu- 
cose preserves  the  fatty  tissues  from  the  influence  of  the 
oxygen,  which  is  consumed  in  the  oxydation  of  the  sugar 
and  the  change  of  the  protein  tissues.     If,  however,  the 
supply  of  farinaceous  food  is  diminished,  the  fat  is  removed 
by  oxydation  faster  than  it  is  deposited,  and  finally  dis- 
appears. 

928.  The  object  of  nutrition,  in  its  wider  sense,  is  to 
supply  the  waste  of  the  tissues,  and  satisfy  the  demands  of 
the  respiratory  process,  thus  preserving  the  balance  of  the 
system.     In  those  animals  that  feed  upon  flesh,  the  fat  con- 
tained in  their  food  or  formed  from  protein,  supplies  the 
wants  of  the  latter  process;  while  in  those  animals  which 
live  upon  vegetables,  or  like  man  upon  a  mixed  diet,  the 
sugar,  alcohol,  and  farinaceous  portions  of  the  food  supply 
more  or  less  completely  the   demands  of  the  respiratory 
process,  and,  if  these  be  in  excess,  the  fat  contained  in  the 
food  often  accumulates  in  the  system. 

The  waste  of  the  muscular,  and  probably  also  of  the 
nervous  substances,  appears  to  sustain  an  intimate  relation  to 
the  amount  of  muscular  and  nervous  activity  of  the  system,* 
while  the  oxydation  of  the  respiratory  elements  is  related  to 
animal  heat.  Respiration  is  essential  to  life,  and  even  in 
those  animals  which  do  not  breathe  air,  the  process  is  ef- 
fected through  oxygen  dissolved  in  the  water.  We  have 

*  The  condition  of  sleep,  in  which  the  muscular  and  nervous  energies 
are  to  a  great  degree  suspended,  probably  sustains  an  important  relation 
t,c  the  nutritive  process,  particularly  as  related  to  the  brain  and  nerves. 
The  different  functions  of  plants  in  light  and  darkness  suggest  an  analog^ 
in  this  connection,  which  is  worthy  of  consideration. 


NUTRITION   OP  PLANTS   AND   ANIMALS.  537 

shown  that  oxygen  is  necessary  to  preserve  the  life  of  the 
blood  corpuscles  out  of  the  body ;  and  it  is  the  deprivation 
of  air  which  causes  the  death  of  animals,  by  preventing  the 
aeration  of  the  corpuscles,  and  destroying  the  vitality  of  the 
blood.  The  introduction  of  large  quantities  of  alcohol  into 
the  system  produces  a  similar  asphyxia,  by  rapidly  con- 
suming the  oxygen,  and  thus  preventing  the  proper  aeration 
of  the  blood.  The  presence  of  phosphuretted  fat,  mentioned 
in  the  analyses  of  the  blood  before  given,  is  said  to  be  confined 
to  the  venous  blood,  which  contains  no  soluble  phosphates ; 
in  the  arterial  blood  the  fat  is  freed  from  phosphorus,  which 
is  found  in  the  form  of  phosphates  in  the  serum. 

929.  The  oxydation  of  carbon  and  hydrogen  compounds, 
converting  them  into  carbonic  acid  and  water,  is  supposed 
to  be  the  source  of  vital  heat  in  animals ;  the  amount  of 
carbon  thus  thrown  off  from  the  lungs  of  a  full-grown  man 
is  equal  to  about  seven  ounces  in  twenty-four  hours.     In 
some  instances  of  disease,  however,  where  the  respiratory 
function  has  been  suspended  for  many  hours,  the  heat  of 
the  body  has  remained  undiminished.     Plants  have  equally 
to  a  certain  extent,  the  power  of  maintaining  a  temperature 
above  that  of  the  atmosphere :  this  is  most  evident  in  the 
leaves  and  young  shoots,  where  vegetation  is  most  active; 
but  in  plants  the  vital  process  is  accompanied  with  a  con- 
stant evolution  of  oxygen,  from  an  action  the  very  reverse 
of  that  which  goes  on  in  animals.    Heat  is  a  common  result 
of  chemical  changes,  even  where  oxygen  is  not  absorbed, 
and  there  is  no  difficulty  in  understanding  its  production  in 
any  of  the  processes  of  assimilation. 

It  is,  however,  probably  true,  that  in  healthy  animals  the 
oxydation  of  carbon  sustains  a  direct  relation  to  the  heat 
evolved.  Hence  it  is  that  in  warm  climates,  where  the  loss 
of  animal  heat  is  small,  farinaceous  matters,  containing  a 
large  amount  of  oxygen,  and  as  it  were,  partly  oxydized, 
are  the  food  of  the  people,  and  are  found  most  congenial  to 
the  taste  j  while  the  inhabitants  of  arctic  regions  consume 
large  quantities  of  fat  and  oil,  less  oxygenized  species  of 
food,  which  are  found  not  only  agreeable,  but  necessary  to 
support  the  demands  of  the  respiratory  process,  and  to  resist 
the  intense  cold. 

930.  The  elements  of  the  food  of  plants  are  taken  from 
the  air,  earth,  and  waters,  and  by  the  forces  of  the  living 
organism  are  formed  into  woody  fibre,,  starch,  sugar,  and 


538  ORGANIC   CHEMISTRY. 

protein,  which  serve  for  fuel  and  for  the  nourishment  01 
animals.  By  the  processes  of  life,  by  combustion  and 
decay,  these  elements  are  again  set  free  in  the  forms  of 
water,  carbonic  acid,  and  ammonia,  and  enter  once  more 
into  the  current  of  organic  life.  In  this  way,  the  results 
of  the  decomposition  of  organic  matters  are  removed  from 
the  atmosphere,  which  would  otherwise  be  vitiated  by  them, 
and  the  carbonic  gas  which  is  taken  up  by  plants,  is  re- 
placed by  an  equal  volume  of  oxygen  gas,  so  that  the  purity 
of  the  air  is  preserved. 

In  the  mutual  dependence  of  the  great  processes  of  animal 
and  vegetable  life  and  decay,  there  is  seen  a  system  in  which 
no  one  process  is  its  own  end,  but  is  implicated  in  every 
other,  and  can  be  understood  only  in  its  relation  to  tho 
Universe,  and  to  that  Being  who  is  at  once  the  efficient  and 
final  Cause  of  all  creation. 


APPENDIX, 


CONTAINING  TABLES  OP  WEIGHTS  AND  MEASURES,  OP  CORRESPOND- 
ING THERMOMETRICAL  DEGREES,  HYDROMETER  TABLES,  STRENGTH 
OF  ALCOHOL,  AND  ANALYSES  OF  WATERS. 


WEIGHTS  AND  MEASURES. 

AVOIRDUPOIS,    OR   IMPERIAL   WEIGHT. 

1  drachm 

16=        1  ounce 

256=       16=       1  pound 

3584=     224=     14=     1  stone 

28672=  1792=  112=     8=  1  hundred  weight... 


Equivalents  in 
Troy  grains. 

27-34 
437-5 
7000- 
98000- 
784000- 


473440=35840=2240=160=20=1  ton 15680000- 


TROT  WEIGHT. 

1  grain. 

24      "     =     1  pennyweight. 
480      "    =  20  "  =  1  ounce. 

6760      "    =240  "  =12     "     : 


:1  pound. 


APOTHECARIES'  WEIGHT. 
1  grain,  gr. 

20      "      =1  scruple,  9 
60      "      =3      "      =1  drachm,  3. 
480      "      =  24      "      =  8      "        =1  ounce,  %. 
6760      "      =288      "      =96      "        =12      "     =1  pound,  Ib. 

539 


540 


APPENDIX. 


APOTHECARIES',  OR  WINE  MEASURE. 
Adopted  in  the  United  States  and  Dublin  Pharmacopoeias. 

Troy  grains  of 
pure  water, 
Cubic  inches.  at  6QO  F. 

1  minim,  trg -00376 =        0-95 

60=       1  fluid-drachm,  f  3 -2256  =       56-95 

480=       8=     1  fluid-ounce,  f g..-..      1-8047  =     455.607 

7680=  128=  16=1  pint,  0 28-8750  =  7289-724 

61440=1024=128=8=1  cong 231-000     =58317-798 

The  imperial  gallon  contains  of  water,  at  60° 70,000-    grains. 

The  pint  (^th  gallon) 8,760-         " 

The  fluid-ounce  (^th  of  pint) 437-5      « 

The  pint  equals  34-66  cubic  inches. 

The  American  standard  gallon  contains  of  pure  water,  at  39 -83°, 
68-372  Troy  grains. 

The  French  kilogramme= 15434-  grains,  or  2-679  Ibs.  Troy,  or 
2-205  Ibs.  avoirdupoids. 

The  gramme =15-4340  grains. 

"    decigramme =  1-5434      " 

"    centigramme =     -1543      " 

"    miligramme =     -0154      " 

The  metre  of  France =39-37      inches. 

"    decimetre =  3-937        " 

"    centimetre =     -394        " 

"    millimetre =     -0394      " 


TABLE    OP   THE    CORRESPONDING   DEGREES    ON   THE    SCALES    OF 
FAHRENHEIT,  REAUMUR,  AND  CENTIGRADE,  OR  CELSIUS. 


Fahr.      Reaum.     Cent. 


212 
203 
194 
185 
176 
167 
158 


80 
76 
72 
68 
64 
60 
56 


100 
95 
90 
85 
80 
75 
70 


Fahr.     Reaum.    Cent.       Fahr.    Reaum.     Cent 


149 

140 

131 

122 

113 

104 

95 

86 

77 

68 

69 


52 
48 
44 
40 
36 
32 
28 
24 
20 
16 
12 


65 
60 
55 
50 
45 
40 
35 
30 
25 
20 
15 


50 
41 
32 
23 
14 
5 
4 
13 
22 
31 
40 


8 

4 

0 

4 

8 

12 

16 

20 

24 

28 

32 


10 
5 
0 
5 

10 
15 
20 
25 
30 
35 
40 


APPENDIX. 


541 


HYDROMETER  TABLES. 

COMPARISON   OF  THE    DEGREES  OP    BATTM^'s   HYDROMETER,  WITH  THB 
REAL  SPECIFIC  GRAVITY. 

1.  For  Liquids  Heavier  than  Water. 


Osg  tea. 

Specific 
gravity. 

Degrees. 

Specific 
gravity. 

Degrees. 

Specific 
gravity. 

Degrees. 

Specific 
grarity. 

0 

1-000 

20 

1-152 

40 

1-357 

60 

1-652 

1 

1.0*7 

21 

1-160 

41 

•369 

61 

1-670 

2 

1-013 

22 

1-169 

42 

•381 

62 

1-689 

3 

1-020 

23 

1-178 

43 

•395 

63 

1-708 

4 

1-027 

24 

1-188 

44 

•407 

64 

1-727 

5 

1-034 

25 

1-197 

45 

•420 

65 

1-747 

6 

1-041 

26 

1-206 

46 

1-434 

66 

1-767 

7 

1-048 

27 

1-216 

47 

1-448 

67 

1-788 

8 

1-056 

28 

1-225 

48 

1-462 

68 

1-809 

9 

1-063 

29 

1-235 

49 

1-476 

69 

1-831 

10 

1-070 

80 

1-245 

50 

1-490 

70 

1-854 

11 

1-078 

31 

1-256 

51 

1-495 

71 

1-877 

12 

1-085 

32 

1-267 

52 

1-520 

72 

1-900 

13 

1-094 

33 

1-277 

53 

1-535 

73 

1-924 

14 

1-101 

34 

1-288 

54 

1-551 

74 

1-949 

15 

1-109 

35 

1-299 

55 

1-567 

75 

1-974 

16 

1-118 

36 

1-310 

56 

1-583 

76 

2-000 

17 

1-126 

37 

1-321 

57 

1-600 

18 

1-134 

38 

1-333 

58 

1-617 

19 

1-143 

39 

1-345 

69 

1-634 

2.  Baume's  Hydrometer  for  Liquids  Lighter  than  Water. 


Degrees. 

Specific 
gravity. 

Degrees. 

Specific 
gravity. 

Degrees. 

Specific 
gravity. 

Degrees. 

Specific 
gravity. 

10 

1-000 

23 

•918 

36 

•849 

49 

•789 

11 

•993 

24 

•913 

37 

•844 

50 

•785 

12 

•986 

25 

•907 

38 

•839 

51 

•781 

13 

•980 

26 

•901 

39 

•834 

52 

•777 

14 

•973 

27 

•896 

40 

•830 

53 

•773 

15 

•967 

28 

•890 

41 

•825 

54 

•768 

16 

•960 

29 

•885 

42 

•820 

55 

•764 

17 

•954 

30 

•880 

43 

•816 

56 

•760 

18 

•948 

31 

•874 

44 

•811 

57 

•757 

19 

•942 

32 

•869 

45 

•807 

58 

•753 

20 

•936 

33 

•864 

46 

•802 

59 

•749 

21 

•930 

34 

•859 

47 

•798 

60 

•745 

22 

•924 

35 

•854 

48 

•794 

642 


APPENDIX. 


TABLES  OF  ANALYSES 

Nos.  1  to  6,  inclusive,  show  the  ingredients  in  1  American  standard 

and  Nos.  9  and 


(1) 

(2) 

(3) 

(4) 

Ingredients. 

Schuylkill 
River. 

Croton 
River. 

Charles 
River. 

Spot 
Pond. 

1 

2 
3 
4 
6 

6 

7 
8 
9 

Chlorid  of  Potassium... 
Chlorid  of  Sodium  
Chlorid  of  Ammonium. 
Chlorid  of  Calcium  
Chlorid  of  Magnesium. 
Chlorid  of  Aluminum... 
Bromid  of  Sodium  
Bromid  of  Magnesium. 

•1470 
•0094 

•167 
•372 
•166 

•1547 
•0420 

•3969 

10 
11 

Sulphate  of  Potash  
Sulphate  of  Soda  

... 

•153 

•3816 

•2276 

1*> 

Sulphate  of  Lime 

•235 

•2624 

13 
14 
15 
16 
17 
18 

Sulphate  of  Magnesia.. 
Sulphate  of  Alumina... 
Nitrate  of  Magnesia.... 
Phosphate  of  Lime  
Phosphate  of  Alumina. 
Alumina  

•0570 

•832 

•0973 

and  iron. 
•1081 

19 

Silicic  Acid  

•0800 

•077 

traces 

traces 

20 
21 
22 
23 
24 
25 
26 
27 

28 

Carbonate  of  Soda  
Carbonate  of  Baryta... 
Carbonate  of  Strontia.. 
Carbonate  of  Lime  
Carbonate  of  Magnesia 
Carbon,  of  Manganese. 
Carbonate  of  Iron  
Fluorid  of  Calcium  
Salts  of  Soda  with  the  ") 
Nitric   and  Organic  L 
Acids  j 

1-8720 
•3510 

1-6436 

2.131 

•662 
traces 

1-865 

•1610 
•0399 

•5291 

•3722 
•1420 

Total  

4-2600 

6-660 

1-6680 

1-2468 

Carbonic  Acid  Gas  in  \ 
cubic  inches  / 
Analyzed  by 

•3879 
Author 

17-418 
Author 

•0464 
Author 

38-79 
Author 

NOTE. — No.  1  is  the  supply  for  the  city  of  Philadelphia,  No.  2 
for  New  York,  and  No.  5  for  Boston  ;  Nos.  4  and  6  are  small  lakes 
in  the  vicinity  of  Boston,  and  No.  3  is  a  river  in  Massachusetts, 
emptying  near  Boston. 


APPENDIX. 


543 


OF  NATURAL  WATERS. 

gallon,  (or  58-372  grains.)  Nos.  7,  8,  and  9  are  in  one  pound  Troy, 
10  in  1000  parts. 


(5) 

(6) 

(7) 

(8) 

(9) 

(10) 

Long 
Pond. 

Mystic 
Pond. 

Saratoga 
C.  Spring. 

Seltzer 
Spring. 

Sea  Water 
Brit.  Chan. 

"Water  of 
Dead  Sea. 

1 

.-0380 

•1590 

1-6256 

•2685 

•7660 

traces 

2 

•0323 

27-911 

19-6653 

12-9690 

27-9590 

78-650 

3 

... 

... 

•0326 

traces 

... 

4 

•0308 

•1544 

... 

28-220 

6 

•0764 

... 

... 

... 

3-666 

60-950 

7 

... 

••• 

•1613 

•  •• 

... 

»*• 

8 

... 

... 

... 

... 

•0290 

7-950 

9 

... 

... 

•0046 

traces 

... 

10 

... 

... 

•1379" 

•2978 

... 

... 

11 

... 

... 

... 

... 

... 

... 

12 

... 

1-2190 

... 

1 

1-4060 

traces 

13 

•1020 

1-9768 

... 

... 

2-2960 

... 

14 

... 

•4478 

... 

... 

... 

... 

15 

... 

... 

•1004 

... 

16 

... 

... 

... 

•0007 

... 

... 

17 

... 

•2810 

... 

•0020 

... 

... 

18 

•0800 

... 

•0069 

... 

... 

19 

•0300 

•5559 

•1112 

•2265 

... 

... 

20 

... 

... 

•8261 

4-6162 

... 

... 

21 

... 

... 

... 

•0014 

... 

22 

... 

... 

•0672 

•0144 

... 

23 

•2380 

•9894 

5-8531 

1-4004 

•0330 

M 

24 

•0630 

•1698 

4-1155 

1-5000 

... 

25 

... 

... 

•0202 

... 

... 

26 

... 

•0173 

... 

27 

... 

... 

... 

•0013 

... 

... 

28 

^  -5295 

... 

... 

... 

... 

... 

1-2220 

32-7671 

34-7452 

21-2982 

35-255 

165-770 

in  100 

c.  in. 

10-719 

10-313 

114- 

126- 

Author. 

Author. 

Schweitzer. 

Struve. 

Schweitzer. 

Author. 

No.  7  is  the  well-known  "Congress  Spring."  No.  8  is  a  cele- 
brated German  Spa. 

No.  10  was  collected  by  J.  D.  Sherwood,  Esq.,  April,  1843, 
near  the  mouth  of  the  Jordan. 


544 


APPENDIX. 


ABSTRACT 

Of  the  Table  of  Lowitz,  showing  the  proportion  by  weight  of  absoiuU 
or  real  alcohol  in  spirits  of  different  densities. 


Sp,  gr.  at  60°. 

Per  cent, 
of  real 
alcohol. 

Sp.gr.  at  60°. 

Per  cent, 
of  real 
alcohol. 

Sp.  gr.  at  60°. 

Per  cent, 
of  real 
alcohol. 

0-796 

100 

0-881 

66 

0-955 

32 

0-798 

99 

0-883 

65 

0-957 

31 

0-801 

98 

0-886 

64 

0-958 

30 

0-804 

97 

0-889 

63 

0-960 

29 

0-807 

96 

0-891 

62 

0-962 

28 

0-809 

95 

0-893 

61 

0-963 

27 

0-812 

94 

0-896 

60 

0-965 

26 

0-815 

93 

0-898 

59 

0-967 

25 

0-817 

92 

0-900 

58 

0-968 

24 

0-820 

91 

0-902 

57 

0-970 

23 

0-822 

90 

0-904 

56 

0-972 

22 

0-825 

89 

0-906 

55 

0-973 

21 

0-827 

88 

0-908 

54 

0974 

20 

0-830 

87 

0-910 

63 

0-975 

19 

0-832 

86 

0-912 

52 

0-977 

18 

0-835 

85 

0-916 

61 

0-978 

17 

0-838 

84 

0-917 

60 

0-979 

16 

0-840 

83 

0-920 

49 

0-981 

15 

0-843 

82 

0-922 

48 

0-982 

14 

0-846 

81 

0-924 

47 

0-984 

13 

0-848 

80 

0-926 

46 

0-986 

12 

0-851 

79 

0-928 

46 

0-987 

11 

0-853 

78 

0-930 

44 

0-988 

10 

0-855 

77 

0-933 

43 

0-989 

9 

0-857 

76 

0-935 

42 

0-990 

8 

0-860 

75 

0-937 

41 

0-991 

7 

0-863 

74 

0-939 

40 

0-992 

6 

0-865 

73 

0-941 

39 

0-867 

72 

0-943 

38 

0-870 

71 

0-945 

37 

0-872 

70 

0-947 

36 

0-874 

69 

0-949 

35 

0-875 

68 

0-951 

34 

0-879 

67 

0-053 

33 

OF  THE 

UNIVERSITY 


INDEX. 


The  references  are  to  the  number*  of  the  sections. 


ACETOL,  736. 

Acetamid,  750. 

Acetates,  744. 

Acetonitryl,  750. 

Acetene,  723. 

Acetene,  perchloric,  725, 

Aceton,  752. 

Acetic  acid,  quick  process  for,  741. 

Acetic  ether,  750. 

Acetic  amylic  ether,  759. 

Acetamid,  686. 

Acid,  acetic,  739 ;  benzoic,  788;  aco- 
nitic,  814;  acrylic,  763;  adipic, 
773;  allophanic,  862;  allanturic, 
873;  alloxanic,  874;  anthropic, 
769  ;  anisic,  795 ;  antimonic,  605  ; 
anthranilic,  843;  amygdalic,  828; 
amalic,  878;  arsenic,  610;  arseni- 
ous,  609;  aspartic,  814;  benzo- 
glycollic,  872;  boraeic,  387;  bro- 
mic,  296;  bromohydric,  430; 
butyric,  764;  camphoric,  800; 
capric,  caproic,  caprylie,  764; 
carbazotic,  790;  carbonic,  366, 
688 ;  carminic,  837;  cerebric,  912  ; 
cerotic,  761 ;  chloracetic,  750 ; 
chloric,  290 ;  chlorochromic,  574  ; 
chlorohydric,  424;  chlorus,  292; 
cholic,  879;  cholalic,  choloidic, 
cholonic,  879 ;  cholelc,  880;  chro- 
mic, 574;  cinn&mic,  796;  citra- 
conic,  814;  citric,  814;  columbic, 
594;  cuminic,  793;  cyanuric, 
856,-dialuric,  876;  elaidic,  769; 
enanthylic,  766;  ethalic,  760; 
evernic,  835;  ferric,  566;  ferro- 
cyanic,  866  ;  fluoboric,  390  ;  fluo- 
hydric,  433 ;  fluosilicic,  385 ;  for- 
mic, 756;  fulminic,  858;  gallic, 
815 ;  glycollic,  871;  hippuric,  871; 
humic,  921;  hydrioclic,  431; 
hydrobromic,  430;  hydrochloric, 
424 ;  hydrocyanic,  844 ;  hydro- 
fluoric, 433;  hydroselenic,  439; 
hydrosulphuric,  435;  hyperiodic, 
301;  hyocholic  and  hyocholalic, 


881 ;  hypochlorous,  291 ;  hypocula- 
ric,  292;  hydrotelluric,  439;  hypo- 
nitric,  345 ;  hypophosphorous,  352; 
iodic,  301;  inosinic,  902;  iodohy- 
dric,431;  isatinic,  843;  kinic,  819; 
lactic,  699 ;  leoanoric  and  lecano- 
rinic,  834;  lithic,  873;  malic,  812; 
manganic,  560;  margaric,  767; 
meconic,  820 ;  metacetonic,  752 ; 
mellisic,  761 ;  malamic,  814 ; 
mesoxalic,  874;  molybdic,  594; 
nitric,  334 ;  nitromuriatic,  429  ; 
nitrophenisic,  790 ;  nitropicric, 
790;  nitroprussic,  868;  nitrosali- 
cylio,  830;  nitrous,  344;  oleic, 
768;  opianic,  820;  orselinic,  or- 
sellic,  834;  oxalic,  807;  oxamic, 
808;  palmitic,  767;  parabonic, 
877;  para-stearic,  767;  pectic, 
704;  pelargonic,  766;  perman- 
ganic, 560;  phocenic,  766;  pyro- 
gallic,  815;  phosphorus,  353; 
phosphoric,  354;  picric,  790; 
pimelie,  773;  pimaric,  803;  pla- 
tinocyanic,  869;  propionic,  752; 
prussic,  844;  pyroligneous,  742; 
quinic,  819;  racemic,  811;  mec- 
onic, 820 ;  ricinoleic,  770  ;  rubery- 
thric,  836 ;  saccharic,  701 ;  sali- 
cylic, 794  and  830  ;  sebacic,  773; 
selenic,  327 ;  selenhydric,  439 ; 
selenious,  327 ;  silicic,  381 ;  stan- 
nic, 597  ;  stearic,  767 ;  suberic, 
succinic,  773 ;  sulphamylic,  758 ; 
sulphomethylic,  754;  sulphotha- 
lic,  760 ;  sulphovinic,  726 ;  sul- 
phindigotic,  842 ;  chloracetic, 
750 ;  sulphocyanic,  851 ;  sulpho- 
benzenic,  789;  sulphydric,  435; 
sulphoglyceric,  764;  sulphurous, 
310  ;  sulphuric,  315  ;  sulphopur- 
puric,  842;  sylvic,  803;  tannic, 
815;  tartaric,  809;  tartramic,  813; 
toluylic,  793 ;  telluhydric,  439  ; 
tellurous,  328;  thionuric,  876; 
titanic,  594;  trigenic,  862; 
545 


546 


INDEX. 


tungstic,  594 ;  ulmic,  711 ;  uric, 
871,  873;  valeric  (valerianic),  759; 
xanthic,  732. 

Acids,  fatty,  list  of,  771 ;  vegetable, 
806;  vinic,  720;  monobasic,  bi- 
basic  and  tribasic,  648;  cou- 
pled, 652;  named,  249;  of  the 
urine  and  of  bile,  871 ;  theory  of, 
481,  646. 

Aconitine,  825. 

Acrolin,  762. 

Affinity,  chemical,  265 ;  circumstan- 
ces which  influence,  268. 

Agriculture,  chemistry  of,  920. 

Air-pump,  22;  syringe,  125. 

Air,  analysis  of,  332. 

Alabaster,  537. 

Alanine,  860. 

Albumin,  animal,  883;  vegetable, 
884. 

Alcohols,  717 ;  products  of  its  oxy- 
dation,  736;  amylic,  758;  me- 
thylic,  753 ;  sulphur,  719. 

Alcohols  and  acids,  relations  of, 
720. 

Aldehyd,  736;  sulphur  aldehyd, 
738. 

Algaroth,  powder  of,  606. 

Alizarine,  836. 

Alkanet,  837. 

Alkalimetry,  497. 

Alkaloids,  of  the  alcohol  series,  776  ; 
vegetal,  816;  of  ammonia,  817; 
of  cinchona,  818;  of  opium,  819. 

Alcargen,  783  ;   alcarsine,  782. 

Allantoine,  873. 

Alazarine,  836. 

Alloxan  and  Alloxantine,  875. 

Alloys,  473. 

Almonds,  essential  oil  of  bitter,  785. 

Alumina,  549 ;  acetate  of,  744 ;  sili- 
cates of,  551 ;  sulphate  of,  550. 

Aluminum,  548. 

Alums,  550. 

Amalgams,  473;  Amalgamation,  191. 

Amarine,  787. 

Ammeline  and  ammelid,  857. 

Amids,  anhydrid,  686. 

Ammonia,  440,  681  ;  origin  of,  441 ; 
acetate  of,  744 ;  bin-iodized,  681 ; 
hydrosulphuret  of,  520;  oxalu- 
rate  of,  877;  present  in  the  at- 
mosphere, 331;  stibethic,  781; 
trichlorinized,  681 ;  salts  of  am- 
monia, 519 ;  water  of,  446 ;  thio- 
nurate  of,  876 ;  salts  of,  683. 

Ammonium,   518;    compounds   of, 


519 ;  cyanid,  846 ;  chlorid  of,  519 ; 
sulphuret  of,  520. 

Ampere's  theory,  203. 

Amygdaline,  828. 

Amylic  ether,  758. 

Amylic  alcohol,  products  of  its  oxyd- 
ation,  759. 

Amylol,  701,  758. 

Amylamine,  778. 

Analysis  of  organic  bodies,  664. 

Anhydrous  sulphuric  acid,  320, 

Aniline,  792 ;  nitric,  792. 

Aneroid  Barometer,  30. 

Anilids,  792. 

Anethol,  795. 

Animal  electricity,  220. 

Animals,  nutrition  of,  915 :  food  of. 
924. 

Anthracite,  712. 

Anthracen,  715. 

Antimony,  604;  oxyds  of,  605; 
chlorids  of,  606;  glass  of,  605; 
sulphurets  of,  607;  tartrate  of, 
and  potash,  607. 

Aphlogistic  lamp,  410. 

Aqua  regia,  429;  ammonise,  446; 
fortis,  334. 

Arbor  Dianse,  627 ;  Saturni,  587. 

Argol,  809. 

Archil,  834. 

Aricine,  819. 

Aragonite,  540. 

Arrowroot,  705. 

Arsenic,  608 ;  as  a  poison,  detection 
of,  613;  chlorid  of,  611;  oxyds 
of,  609 ;  Marsh's  test  for,  6)3 ;  re- 
duction  of,  608;  metallic,  608; 
arsenic  acid,  610;  Reinsch's  test, 
613;  sulphurets  of,  611. 

Arseniuretted  hydrogen,  612. 

Arsine,  782. 

Artesian  wells,  temperature  of,  81. 

Ashes  of  plants,  920. 

Asparagine,  814. 

Atmosphere,  chemical  history  of, 
331 ;  analysis  of,  332 ;  mechanical 
properties  of,  20 ;  weight  of,  26, 
26,  27,  31 ;  determination,  den- 
sity of,  39 ;  limits  of,  32. 

Atomic  weights,  table  of,  238 ;  vo- 
lumes, 260. 

Atoms,  13;  specific  heat  of,  261; 
polarity  of,  42. 

Atropine,  825. 

Attraction  of  gravitation,  10;  che- 
mical, 8  ;  mechanical,  8 ;  capilla- 
ry, 16. 


INDEX. 


5-17 


Aurum  Musivum,  599. 

Azote,  see  Nitrogen,  329. 

Balsams,  796. 

Barium,  526. 

Barometer,  27,  29 ;  Aneroid,  30. 

Barley-sugar,  691. 

Baryta,   527;    carbonate   of,   530; 

nitrate    of,   529;    sulphate    of, 

529. 
Batteries,  galvanic,  190;  Groves', 

195;  Bunsen's,  196;  frog,  221; 

Daniels',  193 ;  Smee's,  192. 
Beeswax,  761. 

Benzamide,  786 ;  Benzoine,  787. 
Benzene,  or  Benzole,  789. 
Benzoline,  787,  825. 
Benzile,  787 ;  Benzonitryl,  788. 
Benzophenon,  793. 
Benzosalicine,  831. 
Benzohelicine,  831. 
Benzoilol,   651,   785;    chlorinized, 

786. 

Bile,  905 ;  acids  of,  879. 
Biliary  calculi,  881. 
Bibasic  acids,  648. 
Bizmuth,  600 ;  oxyd  of,  601 ;  nitrate 

of,  602 ;  fusible  alloy,  603. 
Bituminous  coal,  711. 
Bleaching  powders,  541. 
Blood,  896;  color  and  globules  of, 

900. 
Blowpipe,  compound,  411;  mouth, 

463. 

Blue  pill,  617. 
Boiling,  phenomena  of,  129 ;  in  va- 

cuo,  133 ;  boiling-point,  128 ;  ele- 
vated by  pressure,  136. 
Bones,  913. 
Bouquet  of  wine,  766. 
Boron,  386;  com 

387;  with  hydrogen,  388 ;  chlorid 

of,  389 ;  fluorid  of,  390. 
Borax,  516. 

Brain  and  nervous  matter,  912. 
Bright's  disease,  900. 
British  gum,  705. 
Bromine,  history  of,  294 ;  properties 

of,  295. 

Bromic  ether,  723. 
Brucine,  821. 
Butter  and  butyrine,  butyror  e  764; 

butter  of  antimony,  606. 
Buffy  coafe  of  blood,  900. 
Burning  oil,  797. 
Cadmium,  584. 
Caffeine,  823. 
Calcareous  spar,  540. 


Calcium,  properties  of,  533 ;  chlorid 
of,  536;  fluorid  of,  538;  oxyd  of, 
534. 

Caloric,  79 ;  Calorimetry,  117. 

Calculi,  urinary,  908. 

Calomel,  619. 

Camphene,  797. 

Camphor,  800 ;  Borneo,  801. 

Cane  sugar,  691. 

Candles,  stearine,  772. 

Calculi,  biliary,  881. 

Caoutchouc,  804; 

Capacity  for  heat,  117. 

Capillary  attraction,  16. 

Caprylol,  774. 

Caustic  potash,  489. 

Carbonic  acid,  688  and  366;  lique. 
faction  and  solidification  of,  151; 
how  removed  from  wells,  370 ;  of 
atmosphere,  371;  constitution  of, 
372 ;  theoretical  density  of,  657. 

Carbonic  oxyd,  373  and  689. 

Carthamus  and  carthamine,  837. 

Caprylol,  774. 

Carburetted  hydrogen,  heavy,  450. 
"  "         light,  450. 

Carbon,  357;  bisulphuret  of,  376; 
compounds  with  hydrogen,  450 ; 
nitrogen,  377;  compounds  with 
oxygen,  365 ;  oxyd  of,  373 ;  den- 
sity of  vapor  of,  657 ;  series,  che- 
mistry of,  638. 

Cartesian  devil,  38. 

Castor  oil,  770. 

Casein,  883 ;  vegetable,  884  j  chan- 
ges to  a  peculiar  fat,  890. 

Cathode,  227. 

Catalysis,  271. 

Catalan  forge,  570. 

Catechu,  815. 

Cassius,  purple  of,  631. 

Cellulose,  707. 

Cerium,  556. 

Ceruse,  588. 

Cerotal,  761. 

Chameleon  mineral,  560. 

Charcoal,  362 ;  absorbs  gases,  563 ; 
and  odors,  364. 

Change  of  state  by  heat,  121. 

Chemical  transformations,  642, 

Chloral,  738. 

Chlorimetry,  541. 

Chlorophyle,  838. 

Chemical  affinity,  265  ;  attraction, 
8  ;  nomenclature,  243  ;  philoso^ 
phy,  235. 

Cinchona  bark,  818. 


£48 


INDEX. 


Cinchonine,  818 ;  bichloric  and  bi- 
bromic,  819. 

Chinovatine,  819. 

Chlorine,  preparation,  282 ;  and  pro- 
perties, 284 ;  allotropism  of,  288  ; 
compounds  with  oxygen,  289  ; 
passive  condition,  423. 

Chloroform,  755. 

Chlorocarbonic  oxyd,  375. 

Chlorarsine,  782. 

Cholesterine,  881. 

Chromium,  571;  oxyd  of,  compared, 
572;  chloridof,  574;  compounds 
with  salts  of,  575. 

Citric  acid,  814. 

Citraconid,  814. 

Cinchona,  alkaloids  of,  818. 

Chyle,  906. 

Classification  of  elements,  272. 

Cleavage  of  crystals,  51. 

Coal,  361 ;  gas  from,  456 ;  products 
of  its  distillation,  715. 

Coal  tar,  715. 

Cold,  greatest  natural,  152. 

Cobalt,  580  ;  chlorid  of,  580. 

Cobaltocyanids,  869. 

Codeine,  820. 

Cohesion,  11  and  14;  of  fluids,  15; 
of  gases,  19. 

Colors,  complementary,  70. 

Colomb's  electrometer,  168. 

Collodion,  710. . 

Coloring  matters  described,  833; 
red,  836;  from  lichens,  834;  yel- 
low, 838. 

Columbium  and  Columbite,  594. 

Compounds,  how  named,  243. 

Combination,  mode  of,  in  organic 
bodies,  642. 

Combination,  laws  of,  239 ;  by  vo- 
lume, 257  and  656;  by  direct 
union,  654. 

Combustion,  a  source  of  heat,  80 ; 
nature  of,  457 ;  heat  of,  458 ;  and 
structure  of  flame,  457  and  460. 

Complementary  colors,  70. 

Congelation,  123. 

Conine,  827. 

Conduction  of  heat,  88. 

"  "        in  curves,  90. 

Convection  of  heat,  94. 

Copper,  590 ;  acetate  of,  749 ;  al- 
loys of,  593;  nitrate  of,  593; 
oxyds  of,  591 ;  sulphate  of,  592. 

Cornudum,  549. 

Copal,  803. 


Corpuscles  of  blood  in  frogs  and 
man,  896. 

Cotarnine,  820. 

Corrosive  sublimate,  619. 

Cream,  910. 

Cream  of  tartar,  809. 

Creatine  and  creatinine,  901. 

Cryophorus,  143. 

Crystallization,  circumstances  Influ- 
encing it,  41 ;  nature  of,  40. 

Crystalline  forms,  43. 

Crystals,  measurement  of,  52. 

Culinary  paradox,  134. 

Cupellation,  623. 

Cyanates,  848. 

Cyanids,  844 ;  complex,  866 ;  double, 
853 ;  relations  to  alcohol  series, 
859. 

Cyanid  of  potassium,  846. 

Current,  passage  of  in  cells  of  a  bat- 
tery, 185  ;  strength  of,  186  ;  se- 
condary, 214. 

Cuminal,  793;  Cumene,  793. 

Cudbear,  833. 

Cyamelid,  848. 

Cyanoxosulphid,  851. 

Cyanogen,  377,  847. 

Cyanic  compounds,  844. 

Cyanates,  848. 

Cyanethene,  859. 

Cyaniline,  Cyamelaniline,  and  Cy- 
anharmaline,  863. 

Cyamellurate  of  potash,  852. 

Cymen,  793,  801. 

Daniell's  battery,  193. 

Davy's  safety  lamp,  464. 

Decomposition  of  water,  224,  400. 

Deflagration,  198. 

De  La  Rive's  ring,  205. 

Density  of  vapours,142,656,  and  676. 

Desiccation,  321. 

Daturine,  825. 

Destructive  distillation  of  wood,  713. 

Dew,  formation  of,  144;  point,  144, 

Daniels'  hygrometer,  146. 

Dextrine,  705. 

Diabetes  mellitus,  692,  908. 

Diabetic  sugar,  908. 

Diamond,  history  and  forms  of,  358. 

Diachylon,  plaster,  586,  764. 

Diastase,  706. 

Dicyanid,  perchloric,  855. 

Didymium,  556. 

Diffusion  of  gases  and  vapours,  147 

Digestive  process,  nature  of,  904, 

Dimorphism,  264. 


INDEX. 


549 


Dipping  needle,  160. 

Distillation  of  alcohol,  717. 

Dyslysine,  879. 

Dobereiner's  observation,  409. 

Du  Fay's  hypothesis,  172. 

Dutch  liquid,  454  and  735. 

Earth's  magnetism,  159. 

Eel,  electrical,  222. 

Eggs,  911. 

Elasticity  of  air,  21. 

Electrical  machines,  166. 

Electrical  excitement,  164;  eel,  222; 
polarity,  165. 

Electricity,  153 ;  conductors  of,  169; 
of  high  steam,  178 ;  statical,  163  ; 
distribution  of,  170;  magneto,  217; 
thermo,  218 ;  animal,  220  ;  theo- 
ries of,  172. 

Electricity  of  chemical  action,  179 ; 
effects  of,  197;  constant  light 
from,  200. 

Electro  -  chemical  decomposition, 
223 ;  conditions  of,  228 ;  theory 
of,  233 ;  magnetism,  201 ;  mag- 
netic telegraph,  211 ;  metallurgy, 
234 ;  plating,  870. 

Electro-magnetic  motions,  210,  216. 

Electro-magnets,  207. 

Electrolysis,  227 ;  order  of,  231. 

Electrophorus,  177. 

Electroscopes,  167. 

Electrotype,  234. 

Elements,  denned,  13 ;  table  of,  238; 
laws  of  combination,  235,  239; 
non-metallic,  classified,  272. 

Emetic,  tartar,  607  and  810. 

Emetine,  825. 

Emulsine,  828. 

Endosmose  and  exosmose,  18. 

Epsom  salts,  545. 

Equivalents,  table  of,  238. 

Equivalent  proportions,  239. 

Equivalent  substitution,  643. 

Etna],  ethol,  760. 

Ethammonium,  777. 

Ethamine,  777. 

Ether,  amylic,  758 ;  acetic  amylic, 
759;  butyric,  765;  chloric,  755; 
hydrobromic,  723;  chlorohydric, 
723 ;  hydriodic,  723 ;  hyponitric, 
725  ;  hydrovinic,  727 ;  himinife- 
rous,  55;  lecanoric,  834;  nitric, 
nitrous,  724-5;  oxalic,  808;  per- 
chloric, 725 ;  silicic,  733 ;  sulphu- 
ric, 730. 

Ethers,  723. 

Etherilene  and  etherine,  735. 


Euchlorine,  291. 

Eudiometry.  332;  by  hydrogen. 
405,  407. 

Eupion,  714. 

Evaporation,  140;  influence  of  pres- 
sure on,  141  j  cold  produced  by. 
143. 

Expansion  by  heat,  100 ;  of  solids, 
101;  of  liquids,  100, 102;  of  gases, 
105;  of  water,  103;  beneficial  re* 
suits  of,  104. 

Faraday's  researches  in  magnetism, 
161 ;  in  liquefaction,  150;  in  elec- 
tricity, 227. 

Fats,  and  substances  derived  from 
them,  775. 

Feldspar,  551. 

Fermentation  by  proteine  bodies, 
891  and  694;  butyric,  700;  vis- 
cous,  697. 

Ferricum  and  ferrosum,  649. 

Ferrocyanids,  865. 

Ferricyanids,  867. 

Fibre,  woody,  707. 

Fibrin,  animal  and  vegetable,  882, 
883 ;  change  of,  by  potash,  889 ; 
by  moisture,  Ac.,  890. 

Flame,  structure  of,  460;  of  the 
mouth  blowpipe,  463;  effects  of 
wire  gauze  on,  464. 

Flesh  fluid,  901. 

Fluidity,  121 ;  heat  of,  122. 

Fluorine,  302. 

Fluor-spar,  538. 

Fluids,  properties  of,  15 ;  conduction 
of  heat  in,  92.  . 

Food  of  animals,  924. 

Formene,  tri-chlorinized,  755. 

Formulas,  divisibility  of,  659. 

Franklinian  hypothesis,  172. 

Freezing  mixtures,  124. 

Friction,  a  source  of  heat,  80. 

Frog's  legs,  179,  180,  221. 

Fulminates,  858. 

Fungi  in  fermentation,  695  and  893 

Fousel  oil,  758. 

Fusible  metal,  603. 

Galena,  585. 

Gall-nuts,  815. 

Galvanism,  179;   quantity  and  in 
tensity  in,  186. 

Galvanic  batteries,  190-6. 

Galvanoscopes,  202. 

Gases,  laws  of  the  conduction  of 
heat  in,  93 ;  diffusion  and  efiusioL, 
147;  passage  of  through  mem- 
b  ranee,  149 ;  liquefaction  of,  150 ; 


550 


INDEX. 


management  of,  280 ;  combine  by 

volume,  257. 
Gasholders,  281. 
Gastric  juice,  904. 
Gay  Lussac's  silver  assay,  623. 
Geine,  711. 

Gelatine,  sugar  of,  895. 
Germination  of  seeds,  900. 
German  silver,  579. 
Glass,  552;  manufacture  of,  554. 
Glauber's  salt,  509. 
Glucinum,  556. 
Glucose,  692. 
Gluten,  884. 
Glycerides,  762. 
Glycerine,  762. 
Glycocoll  and  glycooine,  872. 
Gold,  628;  oxyds  and  chlorids  of, 

630  j  wash,  631. 
Goniometer,  common,  52;  Wollas- 

ton's,  53. 

Goulard's  extract,  746. 
Grape  sugar,  692. 
Graphite,  360. 
Grove's  battery,  195. 
Guano,  923. 
Guarana,  823. 

Gum,  703;  elastic,  804  j  resins,  803; 
Gun  cotton,  710. 
Gunpowder,  composition  of,  501. 
Gutta  percha,  805. 
Gypsum,  537. 
Hardness,  14. 
Hare's  blowpipe,  411. 
Harmaline,  863. 
Hartshorn,  445. 
Heat,   79;    communication  of,   83, 

absorption  of,  86 ;  convection  of, 

94 ;  conduction  of,  88 ;  expansion 

by,  100 ;  properties  of,  82 ;  radiant, 

84,  97 ;  solar,  80 ;  sources  of,  80 ; 

specific,  117;  transmission  of,  96; 

latent,  122. 
Heavy  spar,  529. 
Helicine,  830. 

Helix,  204;  contracting,  206. 
Hematosine,  897. 
Hematite,  red  and  brown,  569. 
Hematoxyiine,  837. 
Hemming's  safety  tube,  412. 
Henry's  coils,  magnets,  208,  213. 
Homologous  bodies,  661. 
Honey,  692. 
Horns,  914. 
Humus,  921. 
Hydrobenzamide,  787. 
Hydraulic  line,  535. 


Hydrogen,  391;  properties,  395; 
nature  of,  405 ;  acids,  422 ;  action 
with  chlorine,  423 ;  arseniuretted, 
612;  bromine,  430;  carbon,  450; 
chlorid,  423;  fluorine,  433 ;  iodine, 
431 ;  nitrogen,  440 ;  oxygen,  399 ; 
phosphorus,  448 ;  binoxyd  of,  420; 
selenium,  439;  sulphur,  435;  per- 
oxyd  of,  420 ;  specific  gravity  of, 
295. 

Hydrometer,  37. 

Hydrosulphuret  of  ammonium,  520. 

Hygrometers,  145,  146. 

Hypochlorite  of  lime,  541. 

Hyoscyamine,  825. 

Imponderable  agents,  11. 

indigo,  839. 

Indigogene,  840. 

Induction  of  magnetism,  156 ;  of  a 
secondary  current,  214;  of  elec- 
tricity on  telegraphic  wires,  212. 

Ink,  black,  815 ;  sympathetic,  580. 

Insulators  of  electricity,  169. 

Intensity,  quantity,  186. 

Interference  of  waves,  58,  59. 

lodoform,  755. 

Iodine,  297 ;  compounds  with  oxy- 
gen, 301. 

Ions,  227. 

Iridium,  636. 

Iron,  563;  ferrocyanid,  867;  ores 
of,  569;  pure,  564;  chlorids,  567; 
pyrites,  567;  phosphate,  568; 
acetates,  744;  lactate  of,  700; 
oxyds  of,  566;  reduction  of  ita 
ores,  569;  salts  of,  568 ;  specular, 
566 ;  sulphurets  of,  567. 

Isatine,  843. 

Isinglass,  894. 

Isomerism,  660. 

Isomorphism,  262. 

Kakodyle,  782 ;  protoxyd  of,  783. 

Kermes  mineral,  607. 

Kino,  815. 

Kreasote,  713. 

Kyanite,  551. 

Kyanizing  process,  619. 

Lactates,  lac  tide,  700. 

Lactose,  693. 

Lakes,  550,  836. 

Lamp,Davy's  safety,464;Argand,462. 

Lantanium,  556. 

Lard  oil,  768. 

Laughing  gas,  338. 

Law  of  divisibility  of  formulas,  659. 

Law  of  chemical  transformations, 
642. 


INDEX. 


551 


Lead,  585;  acetates  of,  745,  746; 
carbonate  of,  588 ;  oxyds  of,  586 ; 
plaster  or  diachylon,  586 ;  preci- 
pitated by  zinc,587;  sulphuret,  585. 

Leather,  894. 

Lecanorine,  834. 

Legumen,  884. 

Leiocome,  705. 

Leyden  jar,  173 ;  dissected,  175. 

Leucine,  888. 

Light,  54 ;  interference  of,  59 ;  po- 
larization of,  72;  properties  of, 
61 ;  sources  and  nature  of,  55 ; 
analysis  of,  68  ;  chemical  rays  of, 
75,  76 ;  vibrations  of,  60. 

Lignin,  707. 

Lignite,  712. 

Lime,  534 ;  carbonate  of,  540 ;  hypo- 
chlorid  of,  541 ;  lactate  of,  700 ; 
phosphate  of,  539;  sulphate  of, 
537. 

Liquefaction,  122 ;  and  solidification 
of  gases,  150. 

Liquids,  properties  of,  15,  92. 

Litharge,  586. 

Lithium  and  lithia,  517. 

Litmus,  835. 

Lodestone,  154. 

Logwood,  837. 

Lunar  caustic,  627. 

Luteoline,  838. 

Lymph  globules,  896. 

Madder,  836. 

Magnesia,  543 ;  carbonate  of,  546 ; 
calcined,  543 ;  sulphate  of,  545. 

Magnesian  minerals,  547. 

Magnesium,  542;  chlorid  of,  544; 
oxyd  of,  543. 

Magnetism,  154;  induction  of,  156; 
of  the  earth,  159. 

Magnetics  and  diamagnetics,  161. 

Magnets,  157. 

Magnets,  electro,  207. 

Magneto-electricity,  217. 

Magnus,  green  salt  of,  685. 

Malachite,  green  and  blue,  590. 

Malamid,  814. 

Malt,  action  of  on  sugar,  706. 

Malates,  812. 

Malleability  of  metals,  470. 

Manganese,  557;  chlorids  of,  561; 
oxyds  of,  558;  salts  of,  562. 

Mannite,  693. 

Manures,  920. 

Marble,  540. 

Margarine,  767. 

Mariotte's  law,  24. 


Marsh's  test  for  arsenic,  613. 

Massicot,  586. 

Matter,  general  properties  of,  6; 
divisibility  of,  12. 

Matteucci's  researches,  220. 

Melting-points,  121. 

Mellisol,  761. 

Mellon,  852. 

Melloni's  researches,  97. 

Melam,  852. 

Melamine,  857. 

Melaniline,  863. 

Mercaptan,  719. 

Mercury,  615;  double  amide  of, 
619;  chlorids  of,  619;  fulminate 
of,  858;  iodids  of,  620;  nitrates 
of,  621 ;  oxyds  of,  618 ;  sulphate 
of,  621 ;  sulphurets  of,  620. 

Metacetone,  752. 

Metameric  bodies,  660. 

Metaldehyde,  737. 

Metallurgy,  electro,  234. 

Metals,  general  properties  of,  466 ; 
physical  properties,  469 ;  fusi- 
bility, 121 ;  oxyds  of,  474 ;  che- 
mical relations  of,  474 ;  tenacity 
of,  471. 

Metallic  veins,  467. 

Methol,  753  ;  oxydation  of,  756. 

Methylic  alcohol,  753. 

Methylic  ether,  754. 

Methamine,  778. 

Microscomic  salt,  513. 

Milk,  909  ;  sugar  of,  693. 

Mindereus,  spirit  of,  744. 

Miniums,  586. 

Molecules,  13  ;  polarity  of,  42. 

Molybdenum,  594. 

Monobasic  acids,  648. 

Mordants,  550. 

Morine,  838. 

Morphine,  819. 

Mortar,  535. 

Mouth  blowpipe,  463. 

Murexid,  877  ;  murexoine,  878. 

Muriatic  acid,  428. 

Murray's  solution,  546. 

Muscular  tissue,  887. 

Names  of  elements,  237. 

Nascent  state,  269. 

Naphtha,  716 ;  naphthaline,  715. 

Narcotine  and  narceine,  820. 

Nervous  matter,  912. 

Neutrality  of  salts,  479. 

Newton's  fusible  metal,  603. 

Nickel  and  its  oxyds,  577,  578- 
sulphate,  579. 


552 


INDEX. 


Nicotine  and  nicotianine,  826. 

Nitre,  499  ;  sweet  spirits  of,  725. 

Nitro-prussids,  868. 

Nitrogen,  329 ;  compounds  with 
oxygen,  333  ;  determined  in  or- 
ganic compounds,  672 ;  chlorid 
of,  681. 

Nitrous  oxyd,  338. 

Nitric  oxyd,  341. 

Nitryls,  686. 

Nomenclature  and  symbols,  243. 

Nordhausen  acid,  320. 

Nutritive  substances  containing 
nitrogen,  882. 

Nutrition  of  plants  and  animals, 
915 ;  elements  of,  930. 

(Ersted's  law,  201. 

Ohm's  law,  187. 

-  apparatus  for  compressibility 

of  water,  15. 

Oil  of  bitter  almonds,  785;  of 
fousel,  758  ;  of  castor,  770 ;  of 
mustard,  802;  of  roses,  799;  of 
lard,  767,  797;  of  palm,  767;  of 
potato,  758 ;  of  cumin,  793 ;  of 
cinnamon,  796 ;  of  the  Dutch 
chemists,  735;  of  spirea,  793;  of 
caraway,  citron,  bergamot,  juni- 
per, lemon,  parsley,  798  ;  of  tur- 
pentine, 797 ;  of  winter-green, 
795;  of  vitriol,  319;  of  horse- 
radish, 802. 

Oils,  volatile  or  essential,  796. 

Olefiant  gas,  734,  658;  with  chlo- 
rine, 735. 

Oleine,  767. 

Opium,  alkaloids  of,  819. 

Orcin  and  orceine,  834. 

Ores,  how  distributed,  468. 

Organic  bases  or  alkaloids,  816. 

Organic  bodies  characterized,  637- 
639  ;  general  properties  of,  638  ; 
analysis  of,  664;  modes  of  com- 
bination in,  643  and  following. 

Orpiment,  611. 

Osmium,  636. 

Oxygen,  274 ;  properties  and  ex- 
periments, 277;  allotropic  state, 
279. 

Oxyhydrogen  blowpipe,  411. 

Oxamethane,  808. 

Ozone,  279. 

Palm  oil,  palmatine,  767. 

Palladium,  632. 

Pancreatic  fluid,  903. 

Papaverine,  820. 

Paracyanogen,  853. 


Paranaphthalene,  715. 

Paraffine,  714. 

Pascal's  experiment,  27. 

Pattinson's  process  for  silver,  624. 

Peat,  712. 

Pendulums,  107. 

Peru  balsam,  796. 

Peruvian  bark,  818. 

Pepsin,  904. 

Petalite,  517. 

Petroleum,  716. 

Phene,  789. 

Phenol,  716,  789;  trinitric,  790. 

Phloretine,  phloridzuae,  phlorizein^ 
832. 

Phocenine,  766. 

Phosgene  gas,  689. 

Phosphorescence,  78. 

Phosphoric  acid,  hydrates  of,  355. 

Phosphorus,  346;  red  or  amor- 
phous, 349  ;  chlorids,  bromids, 
356;  compounds  with  oxygen, 
350. 

Phosphuretted  hydrogen,  448. 

Piperin,  picoline,  and  piperidine, 
822. 

Plants,  their  nutrition,  915. 

Platinocyanids,  869. 

Platinum,  633  ;  chlorids  and  oxyds, 
635 ;  power  to  cause  the  union  of 
gases,  409 ;  sponge  and  black, 
634. 

Plumbago,  360. 

Polarization  of  light,  72. 

Polarity,  electrical,  155,  165;  of 
molecules,  42  ;  magnetic,  155. 

Polecat,  secretion  of,  802. 

Populine,  831. 

Polycyanids,  853. 

Polymeric  bodies,  600. 

Potash,  488  ;  acetate  of,  744  ;  aluiui- 
nato  of,  549 ;  carbonates  of,  495, 
496  ;  chlorate,  502 ;  chroraate  of, 
575;  argentocyanid  of,  870;  cy- 
anate,  850;  nitrate,  499  ;  salts  of, 
494 ;  sulphates  of,  498  ;  tartrate 
of,  809  ;  yellow  prussiate,  865  j 
red  prussiate,  867. 

Potassium,  483;  properties,  485;  per- 
oxydof,  487;  tests  for,  490;  sulphu- 
rets,  492  ;  chlorid,  bromid,  and  io- 
did,  491 ;  cyanid,  844,  846 ;  ferri- 
cyanid  of,  867  ;  ferrocyanid,  865  j 
mellonid  of,  852  ;  oxyds  of,  487, 

Potato  oil,  758.  v 

Pottery,  art  of,  555. 

Pneumatic  trough,  280. 


INDEX. 


553 


Presence  of  a  third  body,  271. 

Prussian  blue,  866. 

Pruseic  acid,  844. 

Prussiate  of  potash,  865. 

Prism,  its  action  on  light,  67. 

Prismatic  colors,  69. 

Proteine,  882  ;  relation  to  albumen, 

fibrin,  and  casein,  883 ;  analyses 

and  constitution  of,  887;  changes 

of,  888,  890. 
Pulse  glass,  135. 
Purple  of  Casaius,  631. 
Pyrometer,  114. 
Pyroxylic  spirit,  753. 
Pyroxyline,  710. 
Pyrophorus,  492. 
Quantity  and  intensity,  186. 
Quercitrine,  838. 
Quicksilver,  615. 
Quinine,  818  j  Quinidine,  819. 
Quinoline,  819. 

Racemic  acid,  relations  to  light,  811. 
Radiation, terrestrial,  81;  of  heat,  84. 
Radicals,  salt,  480. 
Ratsbane,  609 ;  realgar,  611. 
Red  lead,  586. 

Red  precipitate,  618.  [63,  64. 

Reflection  and  refraction  of  light, 
Refraction,  index  of,  65 ;  double,  71. 
Rennet,  910. 
Repulsion,  8. 

Residues  of  substitution,  653. 
Resins,  803. 

Reinsch's  arsenic  test,  613. 
Respiration,  926 ;  elements  of,  924. 
Rhodium  and  its  compounds,  636. 
Rochelle  salt,  809. 
Ruthenium,  636. 
Sago  and  salep,  705. 
Safety  lamp,  465. 
Sal-ammoniac,  443. 
Salicine,  794,  829. 
Salicylol  and  its  derivatives,  794, 

829. 

Salicylamid,  795. 
Saligenine,  saliretine,  829. 
Saliva,  903. 
Salts,  theory  of,  477 ;  haloid,  480 ; 

neutrality  of,  479. 
Salt,  common,  508 ;  of  sorrel,  808. 
Salt-radical,  481. 
Saltpetre,  499. 
Sarcosine,  901. 
Sandal  wood,  837. 
Sanguinarine,  825. 
Saxon  blue,  842. 
Secondary  currents,  214. 


Selenium,  325 ;  oxyd  of,  326. 

Selenite,  537. 

Serum  and  seroline,  898. 

Sesqui-oxyds  and  salts,  649. 

Silica,  381. 

Silicic  ethers,  733. 

Silicon,  379;  chlorid  of,  384;  fluo- 
rid  of,  385. 

Silver,  622 ;  oxyds  of,  625 ;  chlorid 
of,  626 ;  nitrate  of,  627;  fulminate 
of,  858. 

Sinamine,  802. 

Smee's  battery,  192. 

Soaps,  764. 

Soda,  507 ;  acetate  of,  744 ;  biborate 
of,  516;  carbonates  of,  510 ;  nitrate 
of,  511 ;  phosphates  of,  512 ;  sili- 
cates of,  552 ;  sulphate  of,  509. 

Sodium,  505 ;  chlorid  of,  508. 

Soils,  relation  of  to  plants,  920. 

Solanine,  825. 

Solids,  properties  of,  14 ;  expansion 
of,  101. 

Solidification  of  gases,  150. 

Solubility  of  sal  soda,  509. 

Soluble  tartar,  809. 

Solution,  267. 

Spathic  iron,  568. 

Specific  gravity,  33 ;   rule  for,  34; 
of  gases,  39. 

Specific  heat  of  bodies,  117. 

Spectrum,  prismatic,  68 ;  fixed  linei 
in,  69. 

Spermaceti,  760. 

Spheroidal  state  of  bodies,  131. 

Spirea  ulmaria,  oil  of,  793. 

Spodumene,  517. 

Spirits  of  wine,  717;  of  nitre,  725. 

Spinel,  549. 

Starch,  705. 

Stalactites,  540. 

Stibethine,  781. 

Steam,  126;  latent  heat  of,  138; 
elastic  force  of,  136 ;  engine,  139. 

Stearin,  767 ;    candles,  772. 

Stearoptens,  800. 

Steel,  570. 

Stibium,  411. 

Strontium,  531 ;  chlorid  of,  532. 

Strychnin,  821. 

Styrax  balsam,  796. 

Substitution,  equivalent,  643. 

Substitution  by  residues,  653. 

Sugar  of  lead,  745 ;  of  gelatin,  895. 

Sugar  of  milk,  693. 

Sugars,  691 ;  products  of  the'j  de- 
composition, 694. 


554 


INDEX. 


Sulphainetbone,  754. 

Bulphamethane,  808. 

Sulphovinie  acid,  726. 

Sulphocyanates,  851. 

Sulphur,  304 ;  compounds  with  oxy- 
gen, 309  ;  chlorid  of,  324. 

Sulphobenzid,  789. 

Sulphur  auratum,  607. 

Sulphuric  acid  manufacture,  318. 

Sulphuretted  hydrogen,  435. 

Surbasic  and  bisurbasio  acetate  of 
lead,  745,  746. 

Sustaining  batteries,  192. 

Symbols,  chemical,  253. 

Tanning,  815. 

Table  of  chemical  equivalents,  238. 

Tannin,  815. 

Tartar  emetic,  810 ;  tartrates,  810  ; 
crude  tartar,  809. 

Tartramid,  813. 

Tapioca,  705. 

Taurine,  880. 

Telegraph,  electro-magnetic,  211. 

Tellurium,  328. 

Temperature  of  flame,  461 ;  of  in- 
candescence, 459. 

Terebol,  799. 

Terpinol,  799. 

Tenacity  of  metals,  471. 

Thebaine,  820. 

Theine,  823 ;  theobromine,  824. 

Thilorier's  apparatus,  151. 

Theories  of  electro-chemical  decom- 
position, 233 ;  of  substitution,  643. 

Thermo-electricity,  218. 

Thermometers,  109 ;  Bregnet's,  115; 
graduation,  111 ;  thermo-electric, 
97 ;  self-registering,  112. 

Thialdin,  793. 

Thorium,  556. 

Thiosinamine,  802. 

Tin,  595 ;  alloys  of,  596 ;  oxyds  of, 
597 ;  chlorids  of,  598,  599. 

Tissues,  waste  of  the  animal,  926  ; 
cellular  and  vascular,  707. 

Titanium,  594. 

Tobacco,  alkaloids  of,  825. 

Tolu,  balsam,  793. 

Toluen,  738. 

Triethamine,  779. 

Tricyanid,  855. 

Touch,  sense  of,  91. 

Tournsol,  834, 

Turmeric,  838. 

TurnbulTs  blue,  867. 

Transmission  of  radiant  heat,  98. 

Tungsten,  594. 


Turpeth  mineral.  621. 

Turpentine,  oil  of,  796. 

Tyrosin,  888. 

Types,  643. 

Ulmine,  711. 

Undulations,  56. 

Upas,  poison  of  the,  821. 

Uramile,  876. 

Uranium,  uranite,  589. 

Urea,  849  ;  vinic,  861 ;  urine,  90* ; 
acids  of,  907. 

Ure's  eudiometer,  405. 

Urinary  calculi,  908. 

Vacuum,  23 ;  Torricellian,  27. 

Valerianates,  759. 

Vanadium,  594. 

Vapor  of  alcohol,  density  of,  718. 

Vaporization,  126. 

Vapors,  maximum  density  of,  142 ; 
density  of  determined,  676. 

Vegetal  acids,  806. 

Vegetable  mould,  711. 

Vegetables,  nutrition  of,  915. 

Vegetal  alkaloids,  816. 

Veratrine,  825. 

Verdigris,  590. 

Vermilion,  620. 

Vibrations  of  light,  60 ;  of  heat. 
89. 

Vinegar,  quick  process  for,  741. 

Vinic  acids,  720. 

Vinol,  717. 

Viacns  fermentation,  694. 

Viscous  fermentation,  697. 

Visible  redness,  459. 

Vitality,  8. 

Vital  heat,  929 ;  force,  639. 

Vitriol,  blue,  592;  green,  568;  oil 
of,  319 ;  white,  583. 

Volatile  alkali,  445. 

Volatile  oils,  796. 

Volta,  his  discoveries,  180. 

Voltaic  pile,  182 ;  circle,  183,  184. 

Voltameter,  226. 

Volume  of  sulphydric  acid,  438; 
combination  by,  257,  656. 

Vulcanized  gum-elastic,  804. 

Waves,  57,  58. 

Water,  history  of,  414,  678 ;  as  a 
chemical  agent,  419  ;  compressi- 
bility of,  15 ;  capacity  for  heat, 
127;  crystalline  forms  of,  415; 
air  in,  416;  solvent  powers  of, 
417;  decomposition  of,  400  ;  vol- 
taic, 224;  formation  of,  397,  401; 
unequal  expansion  of,  103;  bal- 
loon, 38. 


INDEX. 


555 


Water-hammer,  134. 

Wax,  761. 

Weight  and  specific  gravity,  33. 

Wells,  Artesian,  81. 

White  arsenic,  609 ;  lead,  588. 

White  precipitate,  619. 

Wollaston's  goniometer,  53. 

Wood,   destructive  distillation 

713 ;  tar,  714. 
Wood  naphtha,  753. 
Wood  spirit,  753. 


of, 


Woody  fibre,  707;   transformation 

of,  711. 

Xanthine,  836. 
Xyloidine,  710. 
Yeast,  action  of,  892. 
Yellow  prussiate  of  potash,  865. 
Yttrium,  556. 
Zaffre,  580. 
Zinc,  581;  oxyd  of,  583 ;  chlorid  and 

sulphate  of,  583;  lactate  of,  700 
Zirconium,  556. 


OF  THE 

UNIVERSITY 


THS  END. 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 

AN  INITIAL  FINE  OF  25  CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  $1.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


MAR 


18  1941 


LD  21-95m-7,'37 


YB  1 7055 


_84529 


if 


